Method and apparatus for signal acquisition, processing and transmission for evaluation of bodily functions

ABSTRACT

Utilization of a contact device placed on the front part of the eye in order to detect physical and chemical parameters of the body as well as the non-invasive delivery of compounds according to these physical and chemical parameters, with signals preferably being transmitted continuously as electromagnetic waves, radio waves, infrared and the like. One of the parameters to be detected includes non-invasive blood analysis utilizing chemical changes and chemical products that are found in the front part of the eye and in the tear film. A transensor mounted in the contact device laying on the cornea or the surface of the eye is capable of evaluating and measuring physical and chemical parameters in the eye including non-invasive blood analysis. The system preferably utilizes eye lid motion and/or closure of the eye lid to activate a microminiature radio frequency sensitive transensor mounted in the contact device. The signal can be communicated by cable, but is preferably actively or passively radio telemetered to an externally placed receiver. The signal can then be processed, analyzed and stored. Several parameters can be detected including a complete non-invasive analysis of blood components, measurement of systemic and ocular blood flow, measurement of heart rate and respiratory rate, tracking operations, detection of ovulation, detection of radiation and drug effects, diagnosis of ocular and systemic disorders and the like. Other advantages are somnolence awareness, activation of devices by disabled individuals, a new drug delivery system and new therapy for ocular and neurologic disorders, and treatment of cancer in the eye or other parts of the body, and an evaluation system for the overall health status of an individual. The device quantifies non-invasively the amount of the different chemical components in the blood using a contact device with suitable electrodes and membranes laying on the surface of the eye and in direct contact with the tear film or surface of the eye, with the data being preferably transmitted utilizing radio waves, but alternatively sound waves, light waves, wire, or telephone lines can be used for transmission.

This application is a continuing application of application Ser. No.08/707,508, filed Sep. 4, 1996 now U.S. Pat. No. 5,830,139, incorporatedherein in its entirety by references.

FIELD OF THE INVENTION

The present invention includes a contact device for mounting on a partof the body to measure bodily functions and to treat abnormal conditionsindicated by the measurements.

BACKGROUND OF THE INVENTION

The present invention relates to a tonometer system for measuringintraocular pressure by accurately providing a predetermined amount ofapplanation to the cornea and detecting the amount of force required toachieve the predetermined amount of applanation. The system is alsocapable of measuring intraocular pressure by indenting the cornea usinga predetermined force applied using an indenting element and detectingthe distance the indenting element moves into the cornea when thepredetermined force is applied, the distance being inverselyproportional to intraocular pressure. The present invention also relatesto a method of using the tonometer system to measure hydrodynamiccharacteristics of the eye, especially outflow facility.

The tonometer system of the present invention may also be used tomeasure hemodynamics of the eye, especially ocular blood flow andpressure in the eye's blood vessels. Additionally, the tonometer systemof the present invention may be used to increase and measure the eyepressure and evaluate, at the same time, the ocular effects of theincreased pressure.

Glaucoma is a leading cause of blindness worldwide and, although it ismore common in adults over age 35, it can occur at any age. Glaucomaprimarily arises when intraocular pressure increases to values which theeye cannot withstand.

The fluid responsible for pressure in the eye is the aqueous humor. Itis a transparent fluid produced by the eye in the ciliary body andcollected and drained by a series of channels (trabecular meshwork,Schlemm's canal and venous system). The basic disorder in most glaucomapatients is caused by an obstruction or interference that restricts theflow of aqueous humor out of the eye. Such an obstruction orinterference prevents the aqueous humor from leaving the eye at a normalrate. This pathologic condition occurs long before there is a consequentrise in intraocular pressure. This increased resistance to outflow ofaqueous humor is the major cause of increased intraocular pressure inglaucoma-stricken patients.

Increased pressure within the eye causes progressive damage to the opticnerve. As optic nerve damage occurs, characteristic defects in thevisual field develop, which can lead to blindness if the disease remainsundetected and untreated. Because of the insidious nature of glaucomaand the gradual and painless loss of vision associated therewith,glaucoma does not produce symptoms that would motivate an individual toseek help until relatively late in its course when irreversible damagehas already occurred. As a result, millions of glaucoma victims areunaware that they have the disease and face eventual blindness. Glaucomacan be detected and evaluated by measuring the eye's fluid pressureusing a tonometer and/or by measuring the eye fluid outflow facility.Currently, the most frequently used way of measuring facility of outflowis by doing indentation tonography. According to this technique, thecapacity for flow is determined by placing a tonometer upon the eye. Theweight of the instrument forces aqueous humor through the filtrationsystem, and the rate at which the pressure in the eye declines with timeis related to the ease with which the fluid leaves the eye.

Individuals at risk for glaucoma and individuals who will developglaucoma generally have a decreased outflow facility. Thus, themeasurement of the outflow facility provides information which can helpto identify individuals who may develop glaucoma, and consequently willallow early evaluation and institution of therapy before any significantdamage occurs.

The measurement of outflow facility is helpful in making therapeuticdecisions and in evaluating changes that may occur with time, aging,surgery, or the use of medications to alter intraocular pressure. Thedetermination of outflow facility is also an important research tool forthe investigation of matters such as drug effects, the mechanism ofaction of various treatment modalities, assessment of the adequacy ofantiglaucoma therapy, detection of wide diurnal swings in pressure andto study the pathophysiology of glaucoma.

There are several methods and devices available for measuringintraocular pressure, outflow facility, and/or various otherglaucoma-related characteristics of the eye. The following patentsdisclose various examples of such conventional devices and methods:

    ______________________________________                                        U.S.                                                                          PAT. NO.            PATENTEE                                                  ______________________________________                                        5,375,595           Sinha et al.                                              5,295,495           Maddess                                                   5,251,627           Morris                                                    5,217,015           Kaye et al.                                               5,183,044           Nishio et al.                                             5,179,953           Kursar                                                    5,148,807           Hsu                                                       5,109,852           Kaye et al.                                               5,165,409           Coan                                                      5,076,274           Matsumoto                                                 5,005,577           Frenkel                                                   4,951,671           Coan                                                      4,947,849           Takahashi et al.                                          4,944,303           Katsuragi                                                 4,922,913           Waters, Jr. et al.                                        4,860,755           Erath                                                     4,771,792           Seale                                                     4,628,938           Lee                                                       4,305,399           Beale                                                     3,724,263           Rose et al.                                               3,585,849           Grolman                                                   3,545,260           Lichtenstein et al.                                       ______________________________________                                    

Still other examples of conventional devices and/or methods aredisclosed in Morey, Contact Lens Tonometer, RCA Technical Notes, No.602, December 1964; Russell & Bergmanson, Multiple Applications of theNCT: An Assessment of the Instrument's Effect on IOP, Ophthal. Physiol.Opt., Vol. 9, April 1989, pp. 212-214; Moses & Grodzki, ThePneumatonograph: A Laboratory Study, Arch. Ophthalmol., Vol. 97, March1979, pp. 547-552; and C. C. Collins, Miniature Passive PressureTransensor for Implanting in the Eye, IEEE Transactions on Bio-medicalEngineering, April 1967, pp. 74-83.

In general, eye pressure is measured by depressing or flattening thesurface of the eye, and then estimating the amount of force necessary toproduce the given flattening or depression. Conventional tonometrytechniques using the principle of applanation may provide accuratemeasurements of intraocular pressure, but are subject to many errors inthe way they are currently being performed. In addition, the presentdevices either require professional assistance for their use or are toocomplicated, expensive or inaccurate for individuals to use at home. Asa result, individuals must visit an eye care professional in order tocheck their eye pressure. The frequent self-checking of intraocularpressure is useful not only for monitoring therapy and self-checking forpatients with glaucoma, but also for the early detection of rises inpressure in individuals without glaucoma and for whom the elevatedpressure was not detected during their office visit.

Pathogens that cause severe eye infection and visual impairment such asherpes and adenovirus as well as the virus that causes AIDS can be foundon the surface of the eye and in the tear film. These microorganisms canbe transmitted from one patient to another through the tonometer tip orprobe. Probe covers have been designed in order to prevent transmissionof diseases but are not widely used because they are not practical andprovide less accurate measurements. Tonometers which prevent thetransmission of diseases, such as the "air-puff" type of tonometer alsohave been designed, but they are expensive and provide less accuratemeasurements. Any conventional direct contact tonometers can potentiallytransmit a variety of systemic and ocular diseases.

The two main techniques for the measurement of intraocular pressurerequire a force that flattens or a force that indents the eye, called"applanation" and "indentation" tonometry respectively.

Applanation tonometry is based on the Imbert-Fick principle. Thisprinciple states that for an ideal dry, thin walled sphere, the pressureinside the sphere equals the force necessary to flatten its surfacedivided by the area of flattening. P=F/A (where P=pressure, F=force,A=area). In applanation tonometry, the cornea is flattened, and bymeasuring the applanating force and knowing the area flattened, theintraocular pressure is determined.

By contrast, according to indentation tonometry (Schiotz), a knownweight (or force) is applied against the cornea and the intraocularpressure is estimated by measuring the linear displacement which resultsduring deformation or indentation of the cornea. The linear displacementcaused by the force is indicative of intraocular pressure. Inparticular, for standard forces and standard dimensions of the indentingdevice, there are known tables which correlate the linear displacementand intraocular pressure.

Conventional measurement techniques using applanation and indentationare subject to many errors. The most frequently used technique in theclinical setting is contact applanation using Goldman tonometers. Themain sources of errors associated with this method include the additionof extraneous pressure on the cornea by the examiner, squeezing of theeyelids or excessive widening of the lid fissure by the patient due tothe discomfort caused by the tonometer probe resting upon the eye, andinadequate or excessive amount of dye (fluorescein). In addition, theconventional techniques depend upon operator skill and require that theoperator subjectively determine alignment, angle and amount ofdepression. Thus, variability and inconsistency associated with lessvalid measurements are problems encountered using the conventionalmethods and devices.

Another conventional technique involves air-puff tonometers wherein apuff of compressed air of a known volume and pressure is applied againstthe surface of the eye, while sensors detect the time necessary toachieve a predetermined amount of deformation in the eye's surfacecaused by application of the air puff. Such a device is described, forexample, in U.S. Pat. No. 3,545,260 to Lichtenstein et al. Although thenon-contact (air-puff) tonometer does not use dye and does not presentproblems such as extraneous pressure on the eye by the examiner or thetransmission of diseases, there are other problems associated therewith.Such devices, for example, are expensive, require a supply of compressedgas, are considered cumbersome to operate, are difficult to maintain inproper alignment and depend on the skill and technique of the operator.In addition, the individual tested generally complains of painassociated with the air discharged toward the eye, and due to thatdiscomfort many individuals are hesitant to undergo further measurementwith this type of device. The primary advantage of the non-contacttonometer is its ability to measure pressure without transmittingdiseases, but they are not accepted in general as providing accuratemeasurements and are primarily useful for large-scale glaucoma screeningprograms.

Tonometers which use gases, such as the pneumotonometer, have severaldisadvantages and limitations. Such device are also subject to theoperator errors as with Goldman's tonometry. In addition, this deviceuses freon gas, which is not considered environmentally safe. Anotherproblem with this device is that the gas is flammable and as with anyother aerosol-type can, the can may explode if it gets too hot. The gasmay also leak and is susceptible to changes in cold weather, therebyproducing less accurate measurements. Transmission of diseases is also aproblem with this type of device if probe covers are not utilized.

In conventional indentation tonometry (Schiotz), the main source oferrors are related to the application of a relatively heavy tonometer(total weight at least 16.5 g) to the eye and the differences in thedistensibility of the coats of the eye. Experience has shown that aheavy weight causes discomfort and raises the intraocular pressure.Moreover the test depends upon a cumbersome technique in which theexaminer needs to gently place the tonometer onto the cornea withoutpressing the tonometer against the globe. The accuracy of conventionalindentation may also be reduced by inadequate cleaning of the instrumentas will be described later. The danger of transmitting infectiousdiseases, as with any contact tonometer, is also present withconventional indentation.

A variety of methods using a contact lens have been devised, however,such systems suffer from a number of restrictions and virtually none ofthese devices is being widely utilized or is accepted in the clinicalsetting due to their limitations and inaccurate readings. Moreover, suchdevices typically include instrumented contact lenses and/or cumbersomeand complex contact lenses.

Several instruments in the prior art employ a contact lens placed incontact with the sclera (the white part of the eye). Such systems sufferfrom many disadvantages and drawbacks. The possibility of infection andinflammation is increased due to the presence of a foreign body indirect contact with a vascularized part of the eye. As a consequence, aninflammatory reaction around the device may occur, possibly impactingthe accuracy of any measurement. In addition, the level of discomfort ishigh due to a long period of contact with a highly sensitive area of theeye. Furthermore, the device could slide and therefore lose properalignment, and again, preventing accurate measurements to be taken.Moreover, the sclera is a thick and almost non-distensible coat of theeye which may further impair the ability to acquire accurate readings.Most of these devices utilize expensive sensors and complicated electriccircuitry imbedded in the lens which are expensive, difficult tomanufacture and sometimes cumbersome.

Other methods for sensing pressure using a contact lens on the corneahave been described. Some of the methods in this prior art also employexpensive and complicated electronic circuitry and/or transducersimbedded in the contact lens. In addition, some devices usepiezoelectric material in the lens and the metalization of components ofthe lens overlying the optical axis decreases the visual acuity ofpatients using that type of device. Moreover, accuracy is decreasedsince the piezoelectric material is affected by small changes intemperature and the velocity with which the force is applied. There arealso contact lens tonometers which utilize fluid in a chamber to causethe deformation of the cornea; however, such devices lack means foralignment and are less accurate, since the flexible elastic material isunstable and may bulge forward. In addition, the fluid therein has atendency to accumulate in the lower portion of the chamber, thus failingto produce a stable flat surface which is necessary for an accuratemeasurement.

Another embodiment uses a coil wound about the inner surface of thecontact lens and a magnet subjected to an externally created magneticfield. A membrane with a conductive coating is compressed against acontact completing a short circuit. The magnetic field forces the magnetagainst the eye and the force necessary to separate the magnet from thecontact is considered proportional to the pressure. This device suffersfrom many limitations and drawbacks. For example, there is a lack ofaccuracy since the magnet will indent the cornea and when the magnet ispushed against the eye, the sclera and the coats of the eye distorteasily to accommodate the displaced intraocular contents. This occursbecause this method does not account for the ocular rigidity, which isrelated to the fact that the sclera of one person's eye is more easilystretched than the sciera of another. An eye with a low ocular rigiditywill be measured and read as having a lower intraocular pressure thanthe actual eye's pressure. Conversely, an eye with a high ocularrigidity distends less easily than the average eye, resulting in areading which is higher than the actual intraocular pressure. Inaddition, this design utilizes current in the lens which, in turn, is indirect contact with the body. Such contact is undesirable. Unnecessarycost and complexity of the design with circuits imbedded in the lens anda lack of an alignment system are also major drawbacks with this design.

Another disclosed contact lens arrangement utilizes a resonant circuitformed from a single coil and a single capacitor and a magnet which ismovable relative to the resonant circuit. A further design from the samedisclosure involves a transducer comprised of a pressure sensitivetransistor and complex circuits in the lens which constitute theoperating circuit for the transistor. All three of the disclosedembodiments are considered impractical and even unsafe for placement ona person's eye. Moreover, these contact lens tonometers areunnecessarily expensive, complex cumbersome to use and may potentiallydamage the eye. In addition none of these devices permits measurement ofthe applanated area, and thus are generally not very practical.

The prior art also fails to provide a sufficiently accurate technique orapparatus for measuring outflow facility. Conventional techniques anddevices for measuring outflow facility are limited in practice and aremore likely to produce erroneous results because both are subject tooperator, patient and instrument errors.

With regard to operator errors, the conventional test for outflowfacility requires a long period of time during which there can be notilting of the tonometer. The operator therefore must position and keepthe weight on the cornea without moving the weight and without pressingthe globe.

With regard to patient errors, if during the test the patient blinks,squeezes, moves, holds his breath, or does not maintain fixation, thetest results will not be accurate. Since conventional tonography takesabout four minutes to complete and generally requires placement of arelatively heavy tonometer against the eye, the chances of patientsbecoming anxious and therefore reacting to the mechanical weight placedon their eyes is increased.

With regard to instrument errors, after each use, the tonometer plungerand foot plate should be rinsed with water followed by alcohol and thenwiped dry with lint-free material. If any foreign material drys withinthe foot plate, it can detrimentally affect movement of the plunger andcan produce an incorrect reading.

The conventional techniques therefore are very difficult to perform anddemand trained and specialized personnel. The pneumotonograph, besideshaving the problems associated with the pneumotonometer itself, wasconsidered "totally unsuited to tonography." (Report by the Committee onStandardization of Tonometers of the American Academy of Ophthalmology;Archives Ophthalmol., 97:547-552, 1979). Another type of tonometer (NonContact "Air Puff" Tonometer-U.S. Pat. No. 3,545,260) was alsoconsidered unsuitable for tonography. (Ophthalmic & PhysiologicalOptics, 9(2):212-214, 1989). Presently there are no truly acceptablemeans for self-measurement of intraocular pressure and outflow facility.

In relation to an additional embodiment of the present invention, bloodis responsible not only for the transport of oxygen, nutrients, glucose,cholesterol, electrolytes, water, enzymes, white and red blood cells,and genetic markers, but also provides an enormous amount of informationin regards to the overall health status of an individual. The prior artrelated to analysis of blood relies primarily on invasive methods suchas with the use of needles to draw blood for further analysis andprocessing. Very few and extremely limited methods for non-invasiveevaluating blood components are available.

In the prior art for example, oxygenated hemoglobin has been indirectlymeasured by a pulse oximeter based on traditional near infraredabsorption spectroscopy and indirectly measures arterial blood oxygencarried by hemoglobin (not molecular concentration of oxygen) withsensors placed over the skin utilizing LEDs emitting at two wave lengthsaround 940 and 660 nanometers. As the blood oxygenation changes, theratio of the light transmitted by the two frequencies changes indicatingthe amount of oxygenated hemoglobin in the arterial blood of the fingertip. The present systems are not accurate and provide only the amount ofoxygenated hemoglobin in the finger tip.

SUMMARY OF THE INVENTION

In contrast to the various prior art devices, the apparatus of thepresent invention offers an entirely new approach for the measurement ofintraocular pressure and eye hydrodynamics. The apparatus offers asimple, accurate, low-cost and safe means of detecting and measuring theearliest of abnormal changes taking place in glaucoma, and provides amethod for the diagnosis of early forms of glaucoma before anyirreversible damage occurs. The apparatus of this invention provides afast, safe, virtually automatic, direct-reading, comfortable andaccurate measurement utilizing an easy-to-use, gentle, dependable andlow-cost device, which is suitable for home use.

Besides providing a novel method for a single measurement andself-measurement of intraocular pressure, the apparatus of the inventioncan also be used to measure outflow facility and ocular rigidity. Inorder to determine ocular rigidity it is necessary to measureintraocular pressure under two different conditions, either withdifferent weights on the tonometer or with the indentation tonometer andan applanation tonometer. Moreover, the device can perform applanationtonography which is unaffected by ocular rigidity because the amount ofdeformation of the cornea is so very small that very little is displacedwith very little change in pressure. Large variations in ocularrigidity, therefore, have little effect on applanation measurements.

According to the present invention, a system is provided for measuringintraocular pressure by applanation. The system includes a contactdevice for placement in contact with the cornea and an actuationapparatus for actuating the contact device so that a portion thereofprojects inwardly against the cornea to provide a predetermined amountof applanation. The contact device is easily sterilized for multipleuse, or alternatively, can be made inexpensively so as to render thecontact device disposable. The present invention, therefore, avoids thedanger present in many conventional devices of transmitting a variety ofsystemic and ocular diseases.

The system further includes a detecting arrangement for detecting whenthe predetermined amount of applanation of the cornea has been achievedand a calculation unit responsive to the detecting arrangement fordetermining intraocular pressure based on the amount of force thecontact device must apply against the cornea in order to achieve thepredetermined amount of applanation.

The contact device preferably includes a substantially rigid annularmember, a flexible membrane and a movable central piece. Thesubstantially rigid annular member includes an inner concave surfaceshaped to match an outer surface of the cornea and having a hole definedtherein. The subsannular member preferably has a maximum thickness atthe hole and a progressively decreasing thickness toward a periphery ofthe substantially rigid annular member.

The flexible membrane is preferably secured to the inner concave surfaceof the substantially rigid annular member. The flexible membrane iscoextensive with at least the hole in the annular member and includes atleast one transparent area. Preferably, the transparent area spans theentire flexible membrane, and the flexible membrane is coextensive withthe entire inner concave surface of the rigid annular member.

The movable central piece is slidably disposed within the hole andincludes a substantially flat inner side secured to the flexiblemembrane. A substantially cylindrical wall is defined circumferentiallyaround the hole by virtue of the increased thickness of the rigidannular member at the periphery of the hole. The movable central pieceis preferably slidably disposed against this wall in a piston-likemanner and has a thickness which matches the height of the cylindricalwall. In use, the substantially flat inner side flattens a portion ofthe cornea upon actuation of the movable central piece by the actuationapparatus.

Preferably, the actuation apparatus actuates the movable central pieceto cause sliding of the movable central piece in the piston-like mannertoward the cornea. In doing so, the movable central piece and a centralportion of the flexible membrane are caused to project inwardly againstthe cornea. A portion of the cornea is thereby flattened. Actuationcontinues until a predetermined amount of applanation is achieved.

Preferably, the movable central piece includes a magnetically responsiveelement arranged so as to slide along with the movable central piece inresponse to a magnetic field, and the actuation apparatus includes amechanism for applying a magnetic field thereto. The mechanism forapplying the magnetic field preferably includes a coil and circuitry forproducing an electrical current through the coil in a progressivelyincreasing manner. By progressively increasing the current, the magneticfield is progressively increased. The magnetic repulsion between theactuation apparatus and the movable central piece therefore increasesprogressively, and this, in turn, causes a progressively greater forceto be applied against the cornea until the predetermined amount ofapplanation is achieved.

Using known principles of physics, it is understood that the electricalcurrent passing through the coil will be proportional to the amount offorce applied by the movable central piece against the cornea via theflexible membrane. Since the amount of force required to achieve thepredetermined amount of applanation is proportional to intraocularpressure, the amount of current required to achieve the predeterminedamount of applanation will also be proportional to the intraocularpressure.

The calculation unit therefore preferably includes a memory for storinga current value indicative of the amount of current passing through thecoil when the predetermined amount of applanation is achieved and alsoincludes a conversion unit for converting the current value into anindication of intraocular pressure.

The magnetically responsive element is circumferentially surrounded by atransparent peripheral portion. The transparent peripheral portion isaligned with the transparent area and permits light to pass through thecontact device to the cornea and also permits light to reflect from thecornea back out of the contact device through the transparent peripheralportion.

The magnetically responsive element preferably comprises an annularmagnet having a central sight hole through which a patient is able tosee while the contact device is located on the patient's cornea. Thecentral sight hole is aligned with the transparent area of the flexiblemembrane.

A display is preferably provided for numerically displaying theintraocular pressure detected by the system. Alternatively, the displaycan be arranged so as to give indications of whether the intraocularpressure is within certain ranges.

Preferably, since different patients may have different sensitivities orreactions to the same intraocular pressure, the ranges are calibratedfor each patient by an attending physician. This way, patients who aremore susceptible to consequences from increased intraocular pressure maybe alerted to seek medical attention at a pressure less than thepressure at which other less-susceptible patients are alerted to takethe same action.

The detecting arrangement preferably comprises an optical applanationdetection system. In addition, a sighting arrangement is preferablyprovided for indicating when the actuation apparatus and the detectingarrangement are properly aligned with the contact device. Preferably,the sighting arrangement includes the central sight hole in the movablecentral piece through which a patient is able to see while the device islocated on the patient's cornea. The central sight hole is aligned withthe transparent area, and the patient preferably achieves a generallyproper alignment by directing his vision through the central sight holetoward a target mark in the actuation apparatus.

The system also preferably includes an optical distance measuringmechanism for indicating whether the contact device is spaced at aproper axial distance from the actuation apparatus and the detectingarrangement. The optical distance measurement mechanism is preferablyused in conjunction with the sighting arrangement and preferablyprovides a visual indication of what corrective action should be takenwhenever an improper distance is detected.

The system also preferably includes an optical alignment mechanism forindicating whether the contact device is properly aligned with theactuation apparatus and the detecting arrangement. The optical alignmentmechanism preferably provides a visual indication of what correctiveaction should be taken whenever a misalignment is detected, and ispreferably used in conjunction with the sighting arrangement, so thatthe optical alignment mechanism merely provides indications of minoralignment corrections while the sighting arrangement provides anindication of major alignment corrections.

In order to compensate for deviations in corneal thickness, the systemof the present invention may also include an arrangement for multiplyingthe detected intraocular pressure by a coefficient (or gain) which isequal to one for corneas of normal thickness, less than one forunusually thick corneas, and a gain greater than one for unusually thincorneas.

Similar compensations can be made for corneal curvature, eye size,ocular rigidity, and the like. For levels of corneal curvature which arehigher than normal, the coefficient would be less than one. The samecoefficient would be greater than one for levels of corneal curvaturewhich are flatter than normal.

In the case of eye size compensation, larger than normal eyes wouldrequire a coefficient which is less than one, while smaller than normaleyes require a coefficient which is greater than one.

For patients with "stiffer" than normal ocular rigidities, thecoefficient is less than one, but for patients with softer ocularrigidities, the coefficient is greater than one.

The coefficient (or gain) may be manually selected for each patient, oralternatively, the gain may be selected automatically by connecting theapparatus of the present invention to a known pachymetry apparatus whencompensating for corneal thickness, a known keratometer whencompensating for corneal curvature, and/or a known biometer whencompensating for eye size.

The contact device and associated system of the present invention mayalso be used to detect intraocular pressure by indentation. Whenindentation techniques are used in measuring intraocular pressure, apredetermined force is applied against the cornea using an indentationdevice. Because of the force, the indentation device travels in towardthe cornea, indenting the cornea as it travels. The distance traveled bythe indentation device into the cornea in response to the predeterminedforce is known to be inversely proportional to intraocular pressure.Accordingly, there are various known tables which, for certain standardsizes of indentation devices and standard forces, correlate the distancetraveled and intraocular pressure.

Preferably, the movable central piece of the contact device alsofunctions as the indentation device. In addition, the circuit isswitched to operate in an indentation mode. When switched to theindentation mode, the current producing circuit supplies a predeterminedamount of current through the coil. The predetermined amount of currentcorresponds to the amount of current needed to produce one of theaforementioned standard forces.

In particular, the predetermined amount of current creates a magneticfield in the actuation apparatus. This magnetic field, in turn, causesthe movable central piece to push inwardly against the cornea via theflexible membrane. Once the predetermined amount of current has beenapplied and a standard force presses against the cornea, it is necessaryto determine how far the movable central piece moved into the cornea.

Accordingly, when measurement of intraocular pressure by indentation isdesired, the system of the present invention further includes a distancedetection arrangement for detecting a distance traveled by the movablecentral piece, and a computation portion in the calculation unit fordetermining intraocular pressure based on the distance traveled by themovable central piece in applying the predetermined amount of force.

Preferably, the computation portion is responsive to the currentproducing circuitry so that, once the predetermined amount of force isapplied, an output voltage from the distance detection arrangement isreceived by the computation portion. The computation portion then, basedon the displacement associated with the particular output voltage,determines intraocular pressure.

In addition, the present invention includes alternative embodiments, aswill be described hereinafter, for performing indentation-relatedmeasurements of the eye. Clearly, therefore, the present invention isnot limited to the aforementioned exemplary indentation device.

The aforementioned indentation device of the present invention may alsobe utilized to non-invasively measure hydrodynamics of an eye includingoutflow facility. The method of the present invention preferablycomprises several steps including the following:

According to a first step, an indentation device is placed in contactwith the cornea. Preferably, the indentation device comprises thecontact device of the present invention.

Next, at least one movable portion of the indentation device is moved intoward the cornea using a first predetermined amount of force to achieveindentation of the cornea. An intraocular pressure is then determinedbased on a first distance traveled toward the cornea by the movableportion of the indentation device during application of the firstpredetermined amount of force. Preferably, the intraocular pressure isdetermined using the aforementioned system for determining intraocularpressure by indentation.

Next, the movable portion of the indentation device is rapidlyreciprocated in toward the cornea and away from the cornea at a firstpredetermined frequency and using a second predetermined amount of forceduring movement toward the cornea to thereby force intraocular fluid outfrom the eye. The second predetermined amount of force is preferablyequal to or more than the first predetermined amount of force. It isunderstood, however, that the second predetermined amount of force maybe less than the first predetermined amount of force.

The movable portion is then moved in toward the cornea using a thirdpredetermined amount of force to again achieve indentation of thecornea. A second intraocular pressure is then determined based on asecond distance traveled toward the cornea by the movable portion of theindentation device during application of the third predetermined amountof force. Since intraocular pressure decreases as a result of forcingintraocular fluid out of the eye during the rapid reciprocation of themovable portion, it is generally understood that, unless the eye is sodefective that no fluid flows out therefrom, the second intraocularpressure will be less than the first intraocular pressure. Thisreduction in intraocular pressure is indicative of outflow facility.

Next, the movable portion of the indentation device is again rapidlyreciprocated in toward the cornea and away from the cornea, but at asecond predetermined frequency and using a fourth predetermined amountof force during movement toward the cornea. The fourth predeterminedamount of force is preferably equal to or greater than the secondpredetermined amount of force; however, it is understood that the fourthpredetermined amount of force may be less than the second predeterminedamount of force. Additional intraocular fluid is thereby forced out fromthe eye.

The movable portion is subsequently moved in toward the cornea using afifth predetermined amount of force to again achieve indentation of thecornea. Thereafter, a third intraocular pressure is determined based ona third distance traveled toward the cornea by the movable portion ofthe indentation device during application of the fifth predeterminedamount of force.

The differences are then preferably calculated between the first,second, and third distances, which differences are indicative of thevolume of intraocular fluid which left the eye and therefore are alsoindicative of the outflow facility. It is understood that the differencebetween the first and last distances may be used, and in this regard, itis not necessary to use the differences between all three distances. Infact, the difference between any two of the distances will suffice.

Although the relationship between the outflow facility and the detecteddifferences varies when the various parameters of the method and thedimensions of the indentation device change, the relationship for givenparameters and dimensions can be easily determined by known experimentaltechniques and/or using known Friedenwald Tables.

Preferably, the method further comprises the steps of plotting thedifferences between the first, second, and third distance to a create agraph of the differences and comparing the resulting graph ofdifferences to that of a normal eye to determine if any irregularitiesin outflow facility are present.

Additionally, the present invention relates to the utilization of acontact device placed on the front part of the eye in order to detectphysical and chemical parameters of the body as well as the non-invasivedelivery of compounds according to these physical and chemicalparameters, with signals preferably being transmitted continuously aselectromagnetic waves, radio waves, infrared and the like. One of theparameters to be detected includes non-invasive blood analysis utilizingchemical changes and chemical products that are found in the front partof the eye and in the tear film. The non-invasive blood analysis andother measurements are done using the system of my co-pending priorapplication, characterized as an intelligent contact lens system.

The word lens is used here to define an eyepiece which fits inside theeye regardless of the presence of optical properties for correction ofimperfect vision. The word intelligent used here defines a lens capableof signal-detection and/or signal-transmission and/or signal-receptionand/or signal-emission and/or signal-processing and analysis as well asthe ability to alter physical, chemical, and or biological variables.When the device is placed in other parts of the body other than the eye,it is referred to as a contact device or intelligent contact device(ICD).

An alternative embodiment of the present invention will now bedescribed. The apparatus and method is based on a different and novelconcept originated by the inventor in which a transensor mounted in thecontact device laying on the cornea or the surface of the eye is capableof evaluating and measuring physical and chemical parameters in the eyeincluding non-invasive blood analysis. The alternative embodimentpreferably utilizes a transensor mounted in the contact device which ispreferably laying in contact with the surface of the eye and ispreferably activated by the process of eye lid motion and/or closure ofthe eye lid. The system preferably utilizes eye lid motion and/orclosure of the eye lid to activate a microminiature radio frequencysensitive transensor mounted in the contact device. The signal can becommunicated by cable, but is preferably actively or passively radiotelemetered to an externally placed receiver. The signal can then beprocessed, analyzed and stored.

This eye lid force and motion toward the surface of the eye is alsocapable to create the deformation of any transensor/electrodes mountedon the contact device. During blinking, the eye lids are in full contactwith the contact device and the transensor's surface is in contact withthe cornea/tear film and/or inner surface of the eye lid and/or bloodvessels on the surface of the conjunctiva. It is understood that thetransensor used for non-invasive blood analysis is continuouslyactivated when placed on the eye and do not need closure of the eyelidfor activation. It is understood that after a certain amount of time thecontact device will adhere to tissues in the conjunctiva optimizing flowof tissue fluid to sensors for measurement of blood components.

The present invention includes apparatus and methods that utilizes acontact device laying on the surface of the eye called intelligentcontact lens (ICL) which provides means for transmitting physiologic,physical, and chemical information from one location as for instanceliving tissue on the surface of the eye to another remote locationaccurately and faithfully reproducing the event at the receiver. In myprior copending application, the whole mechanism by which the eye lidactivate transensors is described and a microminiature passivepressure-sensitive radio frequency transducer is disclosed tocontinuously measure intraocular pressure and eye fluid outflow facilitywith both open and closed eyes.

The present invention provides a new method and apparatus to detectphysical and chemical parameters of the body and the eye utilizing acontact device placed on the eye with signals being transmittedcontinuously as electromagnetic waves, radio waves, sound waves,infrared and the like. Several parameters can be detected with theinvention including a complete non-invasive analysis of bloodcomponents, measurement of systemic and ocular blood flow, measurementof heart rate and respiratory rate, tracking operations, detection ofovulation, detection of radiation and drug effects, diagnosis of ocularand systemic disorders and the like. The invention also provides a newmethod and apparatus for somnolence awareness, activation of devices bydisabled individuals, a new drug delivery system and new therapy forocular and neurologic disorders, and treatment of cancer in the eye orother parts of the body, and an evaluation system for the overall healthstatus of an individual. The device of the present invention quantifiesnon-invasively the amount of the different chemical components in theblood using a contact device with suitable electrodes and membraneslaying on the surface of the eye and in direct contact with the tearfilm or surface of the eye, with the data being preferably transmittedutilizing radio waves, but alternatively sound waves, light waves, wire,or telephone lines can be used for transmission.

The system comprises a contact device in which a microminiature radiofrequency transensor, actively or passively activated, such asendoradiosondes, are mounted in the contact device which in turn ispreferably placed on the surface of the eye. A preferred method involvessmall passive radio telemetric transducers capable of detecting chemicalcompounds, electrolytes, glucose, cholesterol, and the like on thesurface of the eye. Besides using passive radio transmission orcommunication by cable, active radio transmission with activetransmitters contained a microminiature battery mounted in the contactdevice can also be used.

Several means and transensors can be mounted in the contact device andused to acquire the signal. Active radio transmitters using transensorswhich are energized by batteries or using cells that can be recharged inthe eye by an external oscillator, and active transmitters which can bepowered from a biologic source can also be used and mounted in thecontact device. The preferred method to acquire the signal involvespassive radio frequency transensors, which contain no power source. Theyact from energy supplied to it from an external source. The transensortransmits signals to remote locations using different frequenciesindicative of the levels of chemical and physical parameters. Theseintraocular recordings can then be transmitted to remote extra ocularradio frequency monitor stations with the signal sent to a receiver foramplification and analysis. Ultrasonic micro-circuits can also bemounted in the contact device and modulated by sensors which are capableof detecting chemical and physical changes in the eye. The signal may betransmitted using modulated sound signals particularly under waterbecause sound is less attenuated by water than are radio waves. Thesonic resonators can be made responsive to changes in temperature andvoltage which correlate to the presence and level of molecules such asglucose and ions in the tear film.

Ocular and systemic disorders may cause a change in the pH, osmolarity,and temperature of the tear film or surface of the eye as well as changein the tear film concentration of substances such as acid-lactic,glucose, lipids, hormones, gases, enzymes, inflammatory mediators,plasmin, albumin, lactoferrin, creatinin, proteins and so on. Besidespressure, outflow facility, and other physical characteristics of theeye, the apparatus of the invention is also capable of measuring theabove physiologic parameters in the eye and tear film usingtransensor/electrodes mounted in the contact device. These changes inpressure, temperature, pH, oxygen level, osmolality, concentration ofchemicals, and so on can be monitored with the eyes opened or closed orduring blinking. In some instance such as with the evaluation of pH,metabolites, and oxygen concentration, the device does not neednecessarily eye lid motion because just the contact with the transensormounted in the contact device is enough to activate thetransensor/electrodes.

The presence of various chemical elements, gases, electrolytes, and pHof the tear film and the surface of the eye can be determined by the useof suitable electrodes and a suitable permeable membrane. Theseelectrodes, preferably microelectrodes, can be sensitized by severalreacting chemicals which are in the tear film or the surface of the eye,in the surface of the cornea or preferably the vascularized areas in thesurface of the eye. The different chemicals and substances diffusethrough suitable permeable membranes sensitizing suitable sensors.Electrodes and sensors to measure the above compounds are available fromseveral manufacturers.

The level of oxygen can be measured in the eye with the contact device,and in this case just the placement of the contact device would beenough to activate the system and eye lid motion and/or closure of theeye lid may not be necessary for its operation. Reversible mechanicalexpansion methods, photometric, or electrochemical methods andelectrodes can be mounted in the device and used to detect acidity andgases concentration. Oxygen gas can also be evaluated according to itsmagnetic properties or be analyzed by micro-polarographic sensorsmounted in the contact device. Moreover, the same sensor can measuredifferent gases by changing the cathode potential. Carbon dioxide,carbon monoxide, and other gases can also be detected in a similarfashion.

Microminiature glass electrodes mounted in the contact device can beused to detect divalent cations such as calcium, as well as sodium andpotassium ion and pH. Chloride-ion detector can be used to detect thesalt concentration in the tear film and the surface of the eye. Thesignal can be radio transmitted to a receiver and then to a screen forcontinuous recording and monitoring. This allows for the continuousnon-invasive measurement of electrolytes, chemicals and pH in the bodyand can be very useful in the intensive care unit setting.

A similar transensor can also be placed not in the eye, but in contactwith other mucosas and secretions in the body, such as the oral mucosa,and the concentration of chemicals measured in the saliva or even sweator any other body secretion with signals being transmitted to a remotelocation via ultrasonic or radio waves and the like. However, due to thehigh concentration of enzymes in the saliva and in other secretion, theelectrodes and electronics could be detrimentally affected which wouldimpact accuracy. Furthermore, there is a weak correlation betweenconcentration of chemicals in body secretions and blood.

The tear fluid proves to be the most reliable location and indicator ofthe concentration of chemicals, both organic and inorganic, but otherareas of the eye can be utilized to measure the concentration ofchemicals. The tear fluid and surface of the eye are the preferredlocation for these measurements because the tear film and aqueous humor(which can be transmitted through the intact cornea) can be consideredan ultrafiltrate of the plasma.

The apparatus and method of the present invention allows the leasttraumatic way of measuring chemicals in the body without the need ofneedle stick and the manipulation of blood. For instance, this may beparticularly important as compared to drawing blood from infants becausethe results provided by the drawn blood sample may not be accurate.There is a dramatic change in oxygen and carbon dioxide levels becauseof crying, breath holding and even apnea spells that occur during theprocess of restraining the baby and drawing blood. Naturally, theability to painlessly measure blood components without puncturing thevessel is beneficial also to any adult who needs a blood work-up,patients with diabetes who need to check their glucose level on a dailybasis, and health care workers who would be less exposed to severediseases such as AIDS and hepatitis when manipulating blood. Patients inintensive care units would benefit by having a continuous painlessmonitoring of electrolytes, gases, and so on by non-invasive means usingthe intelligent contact lens system. Moreover, there is no time wastedtransporting the blood sample to the laboratory, the data is availableimmediately and continuously.

The different amounts of eye fluid encountered in the eye can be easilyquantified and the concentration of substances calibrated according tothe amount of fluid in the eye. The relationship between theconcentration of chemical substances and molecules in the blood and theamount of said chemical substances in the tear fluid can be describedmathematically and programmed in a computer since the tear film can beconsidered an ultrafiltrate of the plasma and diffusion of chemicalsfrom capillaries on the surface of the eye have a direct correspondenceto the concentration in the blood stream.

Furthermore, when the eyes are closed there is an equilibrium betweenthe aqueous humor and the tear fluid allowing measurement of glucose ina steady state and since the device can send signals through theintervening eyelid, the glucose can be continuously monitored in thissteady state condition. Optical sensors mounted in the contact devicecan evaluate oxygen and other gases in tissues and can be used to detectthe concentration of compounds in the surface of the eye and thus notnecessarily have to use the tear film to measure the concentration ofsaid substances. In all instances, the signals can be preferably radiotransmitted to a monitoring station. Optical, acoustic, electromagnetic,micro-electromechanical systems and the like can be mounted in thecontact device and allow the measurement of blood components in the tearfilm, surface of the eye, conjunctival vessels, aqueous humor, vitreous,and other intraocular and extraocular structures.

Any substance present in the blood can be analyzed in this way since asmentioned the fluid measured is a filtrate of the blood. Rapidlyresponding microelectrodes with very thin membranes can be used tomeasure these substances providing a continuous evaluation. For example,inhaled anesthetics become blood gases and during an experiment theconcentration of anesthetics present in the blood could be evaluated inthe eye fluid. Anesthetics such as nitrous oxide and halothane can bereduced electrochemically at noble metal electrodes and the electrodescan be mounted in the contact device. Oxygen sensors can also be used tomeasure the oxygen of the sample tear film. Measurement of oxygen andanesthetics in the blood has been performed and correlated well with theamount of the substances in the eye fluid with levels in the tear fluidwithin 85-95% of blood levels. As can be seen, any substances not onlythe ones naturally present, but also artificially inserted in the bloodcan be potentially measured in the eye fluid. A correction factor may beused to account for the differences between eye fluid and blood. Inaddition, the non-invasive measurement and detection by the ICL ofexogenous substances is a useful tool to law enforcement agents forrapidly testing and detecting drugs and alcohol.

The evaluation of systemic and ocular hemodynamics can be performed withsuitable sensors mounted in the contact device. The measurements ofblood pulsations in the eye can be done through electrical means byevaluating changes in impedance. Blood flow rate can be evaluated byseveral techniques including but not limited to ultrasonic andelectromagnetic meters and the signals then radio transmitted to anexternally placed device. For the measurement of blood flow, the contactdevice is preferably placed in contact with the conjunctiva, eitherbulbar or palpebral, due to the fact that the cornea is normally anavascular structure. Changing in the viscosity of blood can also beevaluated from a change in damping on a vibrating quartz micro-crystalmounted in the contact device.

The apparatus of the invention may also measure dimension such as thethickness of the retina, the amount of cupping in the optic nerve head,and so on by having a microminiature ultrasound device mounted in thecontact device and placed on the surface of the eye. Ultra sonictimer/exciter integrated circuits used in both continuous wave andpulsed bidirectional Doppler blood flowmeters are in the order fewmillimeters in length and can be mounted in the apparatus of theinvention.

For the measurement of hemodynamics, the contact device shouldpreferably be placed in contact with the conjunctiva and on top of ablood vessel. Doppler blood microflowmeters are available and continuouswave (CW) and pulsed Doppler instruments can be mounted in the contactdevice to evaluate blood flow and the signal radio transmitted to anexternal receiver. The Doppler flowmeters may also use ultrasonictransducers and these systems can be fabricated in miniature electronicpackages and mounted in the contact device with signals transmitted to aremote receiver.

Illumination of vessels, through the pupil, in the back of the eye canbe used to evaluate blood flow velocity and volume or amount of cupping(recess) in the optic nerve head. For this use the contact device hasone or more light sources located near the center and positioned in away to reach the vessels that exit the optic nerve head, which are thevessels of largest diameter on the surface of the retina. A precisealignment of beam is possible because the optic nerve head is situatedat a constant angle from the visual axis. Sensors can be also positionedon the opposite side of the illumination source and the reflected beamreaching the sensor. Multioptical filters can be housed in the contactdevice with the light signal converted to voltage according to the angleof incidence of reflected light. Moreover, the intracranial pressurecould be indirectly estimated by the evaluation of changes and swellingin the retina and optic nerve head that occurs in these structures dueto the increased intracerebral pressure.

Fiber optics from an external light source or light sources built in thecontact device can emit a beam of plane-polarized light from one side atthree o'clock position with the beam entering through the cornea andpassing through the aqueous humor and exiting at the nine o'clockposition to reach a photodetector. Since glucose can rotate the plane ofpolarization, the amount of optical rotation would be compared to asecond reference beam projected in the same manner but with a wavelengththat it is insensitive to glucose with the difference being indicativeof the amount of glucose present in the aqueous humor which can becorrelated to plasma glucose by using a correction factor.

A dielectric constant of several thousand can be seen in blood and amicrominiature detector placed in the contact device can identify thepresence of blood in the surface of the cornea. Moreover, blood causesthe decomposition of hydrogen peroxide which promotes an exothermicreaction that can be sensed with a temperature-sensitive transensor.Small lamps energized by an external radio-frequency field can bemounted in the contact device and photometric blood detectors can beused to evaluate the presence of blood and early detection ofneovascularization in different parts of the eye and the body.

A microminiature microphone can be mounted in the contact device andsounds from the heart, respiration, flow, vocal and the environment canbe sensed and transmitted to a receiver. In cases of abnormal heartrhythm, the receiver would be carried by the individual and will havemeans to alert the individual through an alarm circuit either by lightor sound signals of the abnormality present. Changes in heart beat canbe detected and the patient alerted to take appropriate action.

The contact device can also have elements which produce and radiaterecognizable signals and this procedure could be used to locate andtrack individuals, particularly in military operations. A permanentmagnet can also be mounted in the contact device and used for trackingas described above.

Life threatening injuries causing change in heart rhythm and respirationcan be detected since the cornea pulsates according to heartbeat. Motionsensitive microminiature radio frequency transensors can be mounted inthe contact device and signals indicative of injuries can be radiotransmitted to a remote station particularly for monitoring duringcombat in military operations.

In rocket or military operations or in variable g situations, theparameters above can be measured and monitored by utilizing materials inthe transensor such as light aluminum which are less sensitive togravitational and magnetic fields. Infrared emitters can be mounted inthe contact device and used to activate distinct photodetectors byocular commands such as in military operations where fast action isneeded without utilizing hand movement.

Spinal cord injuries have lead thousands of individuals to completeconfinement in a wheel chair. The most unfortunate situation occurs withquadriplegic individuals who virtually only have useful movement oftheir mouth and eyes. The apparatus of the invention allows theseindividuals to use their remaining movement ability to become moreindependent and capable of indirect manipulation of a variety ofhardware. In this embodiment, the ICL uses blinking or closure of theeyes to activate remotely placed receptor photodiodes through theactivation of an LED drive coupled with a pressure sensor.

The quadriplegic patient focuses on a receptor photo diode and closestheir eyes for 5 seconds, for example. The pressure exerted by theeyelid is sensed by the pressure sensor which is coupled with a timingchip. If the ICL is calibrated for 5 sec, after this amount of timeelapses with eyes closed, the LED drive activates the LED which emitsinfrared light though the intervening eyelid tissue reaching suitablereceptor photodiodes or suitable optical receivers connected to a poweron or off circuit. This allows quadriplegics to turn on, turn off, ormanipulate a variety of devices using eye motion. It is understood thatan alternative embodiment can use more complex integrated circuitsconnected by fine wires to the ICL placed on the eye in order to performmore advanced functions such as using LED's of different wavelengths.

Another embodiment according to the present invention includes asomnolence alert device using eye motion to detect premonitory signs ofsomnolence related to a physiologic condition called Bell phenomena inwhich the eye ball moves up and slightly outwards when the eyes areclosed. Whenever an individual starts to fall asleep, the eye lid comesdown and the eyes will move up.

A motion or pressure sensor mounted in the superior edge of the ICL willcause, with the Bell phenomena, a movement of the contact deviceupwards. This movement of the eye would position the pressure sensitivesensor mounted in the contact device against the superior cul-de-sac andthe pressure created will activate the sensor which modulates a radiotransmitter. The increase in pressure can be timed and if the pressureremains increased for a certain length of time indicating closed eyes,an alarm circuit is activated. The signal would then be transmitted to areceiver coupled with an alarm circuit and speaker creating a soundsignal to alert the individual at the initial indication of fallingasleep. Alternatively, the pressure sensor can be positioned on theinferior edge of the ICL and the lack of pressure in the inferiorlyplaced sensor would activate the circuit as described above.

It is also understood that other means to activate a circuit in thecontact device such as closing an electric circuit due to motion orpressure shift in the contact device which remotely activate an alarmcan be used as a somnolence awareness device. It is also understood thatany contact device with sensing elements capable of sensing Bellphenomena can be used as a somnolence awareness device. This system,device and method are an important tool in diminishing car accidents andmachinery accidents by individuals who fall sleep while operatingmachinery and vehicles.

If signs of injury in the eye are detected, such as increasedintraocular pressure (IOP), the system can be used to release medicationwhich is placed in the cul-de-sac in the lower eye lid as a reservoir orpreferably the contact lens device acts as a reservoir for medications.A permeable membrane, small fenestrations or a valve like system withmicro-gates, or micro-electronic systems housed in the contact devicestructure could be electrically, magnetically, electronically, oroptically activated and the medication stored in the contact devicereleased. The intelligent lenses can thus be used as non-invasive drugdelivery systems. Chemical composition of the tear film, such as thelevel of electrolytes or glucose, so that can be sensed and signalsradio transmitted to drug delivery pumps carried by the patient so thatmedications can be automatically delivered before symptoms occur.

A part of the contact transducer can also be released, for instance ifthe amount of enzymes increases. The release of part of the contactdevice could be a reservoir of lubricant fluid which will automaticallybe released covering the eye and protecting it against the insultingelement. Any drugs could be automatically released in a similar fashionor through transmission of signal to the device.

An alternative embodiment includes the contact device which has acompartment filled with chemical substances or drugs connected to athread which keeps the compartments sealed. Changes in chemicals in thetear fluid or the surface of the eye promote voltage increases whichturns on a heater in the circuit which melts the thread allowingdischarge of the drug housed in the compartment such as insulin if thereis an increase in the levels of glucose detected by the glucose sensor.

To measure temperature, the same method and apparatus applies, but inthis case the transmitter is comprised of a temperature-sensitiveelement. A microminiature temperature-sensitive radio frequencytransensor, such as thermistor sensor, is mounted in the contact devicewhich in turn is placed on the eye with signals preferably radiotransmitted to a remote station. Changes in temperature and body heatcorrelate with ovulation and the thermistor can be mounted in thecontact device with signals telemetered to a remote station indicatingoptimum time for conception.

The detection and transmission to remote stations of changes intemperature can be used on animals for breeding purposes. Theintelligent contact lens can be placed on the eye of said animals andcontinuous monitoring of ovulation achieved. When this embodiment isused, the contact device with the thermistor is positioned so that itlodges against the palpebral conjunctiva to measure the temperature atthe palpebral conjunctiva. Monitoring the conjunctiva offers theadvantages of an accessible tissue free of keratin, a capillary levelclose to the surface, and a tissue layer vascularized by the samearterial circulation as the brain. When the lids are closed, the thermalenvironment of the cornea is exclusively internal with passiveprevention of heat loss during a blink and a more active heat transferduring the actual blink.

In carotid artery disease due to impaired blood supply to the eye, theeye has a lower temperature than that of the fellow eye which indicatesa decreased blood supply. If a temperature difference greater thannormal exists between the right and left eye, then there is an asymmetryin blood supply. Thus, this embodiment can provide information relatedto carotid and central nervous system vascular disorders. Furthermore,this embodiment can provide information concerning intraocular tumorssuch as melanoma. The area over a malignant melanoma has an increase intemperature and the eye harboring the malignant melanoma would have ahigher temperature than that of the fellow eye. In this embodiment thethermistor is combined with a radio transmitter emitting an audio signalfrequency proportional to the temperature.

Radiation sensitive endoradiosondes are known and can be used in thecontact device to measure the amount of radiation and the presence ofradioactive corpuscules in the tear film or in front of the eye whichcorrelates to its presence in the body. The amount of hydration andhumidity of the eye can be sensed with an electrical discharge andvariable resistance moisture sensor mounted in the contact device.Motion and deceleration can be detected by a mounted accelerometer inthe contact device. Voltages accompanying the function of the eye,brain, and muscles can be detected by suitable electrodes mounted in thedevice and can be used to modulate the frequency of the transmitter. Inthe case of transmission of muscle potentials, the contact device isplaced not on the cornea, but next to the extraocular muscle to beevaluated and the signals remotely transmitted. A fixed frequencytransmitter can be mounted in the contact device and used as a trackingdevice which utilizes a satellite tracking system by noting thefrequency received from the fixed frequency transmitter to a passingsatellite

A surface electrode mounted in the contact device may be activated byoptical or electromagnetic means in order to increase the temperature ofthe eye. This increase in temperature causes a dilation of the capillarybed and can be used in situations in which there is hypoxia (decreasedoxygenation) in the eye. The concept and apparatus called heatstimulation transmission device (HSTD) is based upon my experiments andin the fact that the eye has one of largest blood supply per gram oftissue in the body and has the unique ability to be overpefused whenthere is an increase in temperature. The blood flow to the eye can thusbe increased with a consequent increase in the amount of oxygen. Theelectrode can be placed in any part of the eye, inside or outside, butis preferably placed on the most posterior part of the eye. The radiofrequency activated heating elements can be externally placed orsurgically implanted according to the area in need of increase in theamount of oxygen in the eye. It is understood that the same heatingelements could be placed or implanted in other parts of the body.Naturally, means that promote an increase in temperature of the eyewithout using electrodes can be used as long as the increase intemperature is sufficient to increase blood flow without promoting anyinjury.

The amount of increase varies from individual to individual andaccording to the status of the vascular bed of the eye. The increase intemperature of blood in the eye raises its oxygen level about 6% pereach one degree Celsius of increase in temperature allowing precisequantification of the increase in oxygen by using a thermistor whichsimultaneously indicates temperature, or alternatively an oxygen sensorcan be used in association with the heating element and actual amount ofincrease in oxygen detected.

This increase in blood flow can be timed to occur at predetermined hoursin the case of chronic hypoxia such as in diabetes, retinaldegenerations, and even glaucoma. These devices can be externally placedor surgically implanted in the eye or other parts of the body accordingto the application needed.

Another embodiment is called over heating transmission device (OHTD) andrelates to a new method and apparatus for the treatment of tumors in theeye or any other part of the body by using surgically implanted orexternally placed surface electrodes next to a tumor with the electrodesbeing activated by optical or electromagnetic means in order to increasethe temperature of the cancerous tissue until excessive localized heatdestroys the tumor cells. These electrodes can be packaged with athermistor and the increase in temperature sensed by the thermistor withthe signal transmitted to a remote station in order to evaluate thedegree of temperature increase. The OHTD includes means to detect normalfrom abnormal tissue by labeling with the increase in temperatureextending only to the abnormal tissue. Furthermore, sensors sensitive tonecrotic products can be used to quantify the amount of tissuedegradation.

Another embodiment concerning therapy of eye and systemic disordersinclude a neuro-stimulation transmission device (NSTD) which relates toa system in which radio activated micro-photodiodes or/andmicro-electric circuits and electrodes are surgically implanted orexternally placed on the eye or other parts of the body such as thebrain and used to electrically stimulate non-functioning neural ordegenerated neural tissue in order to treat patients with retinaldegeneration, glaucoma, stroke, and the like. Multiple electrodes can beused in the contact device, placed on the eye or in the brain forelectrical stimulation of surrounding tissues with consequentregeneration of signal transmission by axonal and neural cells andregeneration of action potential with voltage signals being transmittedto a remote station.

Radio and sonic transensors to measure pressure, electrical changes,dimensions, acceleration, flow, temperature, bioelectric activity andother important physiologic parameters and power switches to externallycontrol the system have been developed and are suitable systems to beused in the apparatus of the invention. The sensors can be automaticallyturned on and off with power switches externally controlling theintelligent contact lens system. The use of integrated circuits andadvances occurring in transducer, power source, and signal processingtechnology allow for extreme miniaturization of the components whichpermits several sensors to be mounted in one contact device. Forinstance, typical resolutions of integrated circuits are in the order ofa few microns and very high density circuit realization can be achieved.Radio frequency and ultrasonic microcircuits are available and can beused and mounted in the contact device. A number of different ultrasonicand pressure transducers are also available and can be used and mountedin the contact device.

Technologic advances will occur which allow full and novel applicationsof the apparatus of the invention such as measuring enzymatic reactionsand DNA changes that occur in the tear fluid or surface of the eye, thusallowing an early diagnosis of disorders such as cancer and heartdiseases. HIV virus is present in tears and AIDS could be detected withthe contact device by sensors coated with antibodies against the viruswhich would create a photochemical reaction with appearance ofcolorimetric reaction and potential shift in the contact device withsubsequent change in voltage or temperature that can be transmitted to amonitoring station.

A variety of other pathogens could be identified in a similar fashion.These signals can be radio transmitted to a remote station for furthersignal processing and analysis. In the case of the appearance offluorescent light, the outcome could be observed on a patient's eyesimply by illuminating the eye with light going through a cobalt filterand in this embodiment the intelligent contact lens does not need tonecessarily have signals transmitted to a station.

The system further comprises a contact device in which a microminiaturegas-sensitive, such as oxygen-sensitive, radio frequency transensor ismounted in the contact device which in turn is placed on the corneaand/or surface of the eye. The system also comprises a contact device inwhich a microminiature blood velocity-sensitive radio frequencytransensor is mounted in the contact device which in turn is placed onthe conjunctiva and is preferably activated by eye lid motion and/orclosure of the eye lid. The system also comprises a contact device inwhich a radio frequency transensor capable of measuring the negativeresistance of nerve fibers is mounted in the contact device which inturn is preferably placed on the cornea and/or surface of the eye. Bymeasuring the electrical resistance, the effects of microorganisms,drugs, poisons and anesthetics can be evaluated. The system alsocomprises a contact device in which a microminiature radiation-sensitiveradio frequency transensor is mounted in the contact device which inturn is preferably placed on the cornea.

The contact device preferably includes a rigid or flexible annularmember in which a transensor is mounted in the device. The transensor ispositioned in a way to allow passage of light trough the visual axis.The annular member preferably includes an inner concave surface shapedto match an outer surface of the eye and having one or more holesdefined therein in which transensors are mounted. It is understood thatthe contact device conforms in general shape to the surface of the eyewith its dimensions and size chosen to achieve optimal comfort level andtolerance. It is also understood that the curvature and shape of thecontact device is chosen to intimately and accurately fit the contactdevice to the surface of the eye for optimization of sensor function.The surface of the contact device can be porous or microporous as wellas with mircro-protuberances on the surface. It is also understood thatfenestrations can be made in the contact device in order to allow betteroxygenation of the cornea when the device is worn for a long period oftime. It is also understood that the shape of the contact device mayinclude a ring-like or band-like shape without any material covering thecornea. It is also understood that the contact device may have a basedown prism or truncated edge for better centration. It is alsounderstood that the contact device preferably has a myofiange or a minuscarrier when a conventional contact lens configuration is used. It isalso understood that an eliptical half moon shape or the like can beused for placement under the eyelid. It is understood that the contactdevice can be made with soft of hard material according to theapplication needed. It is also understood that an oversized cornealscleral lens covering the whole anterior surface of the eye can be usedas well as hourglass shaped lenses and the like. It is understood alsothat the external surface of the contact device can be made withpolymers which increases adherence to tissues or coating which increasesfriction and adherence to tissues in order to optimize fluid passage tosensors when measuring chemical components. It is understood that thedifferent embodiments which are used under the eyelids are shaped to fitbeneath the upper and/or eyelids as well as to fit the upper or lowercul-de-sac.

The transensor may consist of a passive or active radio frequencyemitter, or a miniature sonic resonator, and the like which can becoupled with miniature microprocessor mounted in the contact device. Thetransensors mounted in the contact device can be remotely driven byultrasonic waves or alternatively remotely powered by electromagneticwaves or by incident light. They can also be powered by microminiaturelow voltage batteries which are inserted into the contact device.

As mentioned, preferably the data is transmitted utilizing radio waves,sound waves, light waves, by wire, or by telephone lines. The describedtechniques can be easily extrapolated to other transmission systems. Thetransmitter mounted in the contact device can use the transmission linksto interconnect to remote monitoring sites. The changes in voltage orvoltage level are proportional to the values of the biological variablesand this amplified physiologic data signal from the transducers may befrequency modulated and then transmitted to a remote external receptionunit which demodulates and reconstitutes the transmitted frequencymodulated data signal preferably followed by a low pass filter with theregeneration of an analog data signal with subsequent tracing on astrip-chart recorder.

The apparatus of the invention can also utilize a retransmitter in orderto minimize electronic components and size of the circuit housed in thecontact device. The signal from a weak transmitter can be retransmittedto a greater distance by an external booster transmitter carried by thesubject or placed nearby. It is understood that a variety of noisedestruction methods can be used in the apparatus of the invention.

Since the apparatus of the invention utilizes externally placed elementson the surface of the eye that can be easily retrieved, there is notissue damage due to long term implantation and if drift occurs it ispossible to recalibrate the device. There are a variety of formats thatcan be used in the apparatus of the invention in which biologic data canbe encoded and transmitted. The type of format for a given applicationis done according to power requirement, circuit complexity, dimensionsand the type of biologic data to be transmitted. The general layout ofthe apparatus preferably includes an information source with a varietyof biological variables, a transducer, a multiplexer, a transmitter, atransmission path and a transmission medium through which the data istransmitted preferably as a coded and modulated signal.

The apparatus of the invention preferably includes a receiver whichreceives the coded and modulated signal, an amplifier and low passfilter, a demultiplexer, a data processing device, a display andrecording equipment, and preferably an information receiver, a CPU, amodem, and telephone connection. A microprocessor unit containing anautodialing telephone modem which automatically transmits the data overthe public telephone network to a hospital based computer system can beused. It is understood that the system may accept digitally codedinformation or analog data.

When a radio link is used, the contact device houses a radio frequencytransmitter which sends the biosignals to a receiver located nearby withthe signals being processed and digitized for storage and analysis bymicrocomputer systems. When the apparatus of the invention transmitsdata using a radio link, a frequency carrier can be modulated by asubcarrier in a variety of ways: amplitude modulation (AM), frequencymodulation (FM), and code modulation (CM). The subcarriers can bemodulated in a variety of ways which includes AM, FM, pulse amplitudemodulation (PAM), pulse duration modulation (PDM), pulse positionmodulation (PPM), pulse code modulation (PCM), delta modulation (DM),and the like.

It is understood that the ICL structure and the transducer/transmitterhousing are made of material preferably transparent to radio waves andthe electronic components coated with materials impermeable to fluidsand salts and the whole unit encased in a biocompatable material. Theelectronics, sensors, and battery (whenever an active system is used),are housed in the contact device and are hermetically sealed againstfluid penetration. It is understood that sensors and suitable electrodessuch as for sensing chemicals, pH and the like, will be in directcontact with the tear fluid or the surface of the eye. It is alsounderstood that said sensors, electrodes and the like may be coveredwith suitable permeable membranes according to the application needed.The circuitry and electronics may be encased in wax such as beeswax orparaffin which is not permeable to body fluid. It is understood thatother materials can be used as a moisture barrier. It is also understoodthat various methods and materials can be used as long as there isminimal frequency attenuation, insulation, and biocompatibility. Thecomponents are further encased by biocompatible materials as the onesused in conventional contact lenses such as Hydrogel, silicone, flexibleacrylic, sylastic, or the like.

The transmitter, sensors, and other components can be mounted and/orattached to the contact device using any known attachment techniques,such as gluing, heat-bonding, and the like. The intelligent contact lenscan use a modular construction in its assembly as to allow tailoring thenumber of components by simply adding previously constructed systems tothe contact device.

It is understood that the transmission of data can be accomplished usingpreferably radio link but other means can also be used. The choice ofwhich energy form to be used by the ICL depends on the transmissionmedium and distance, channel requirement, size of transmitter equipmentand the like. It is understood that the transmission of data from thecontact device by wire can be used but has the disadvantage ofincomplete freedom from attached wires. However, the connection ofsensors by wires to externally placed electronics, amplifiers, and thelike allows housing of larger sensors in the contact device when theapplication requires as well as the reduction of mechanical andelectrical connections in the contact device. The transmission of databy wire can be an important alternative when there is congested spacedue to sensors and electronics in the contact device. It is understoodthat the transmission of data in water from the contact device can bepreferably accomplished using sound energy with a receiver preferablyusing a hydrophone crystal followed by conventional audio frequency FMdecoding.

It is also understood that the transmission of data from the contactdevice can be accomplished by light energy as an alternative to radiofrequency radiation. Optical transmission of signals using all sorts oflight such as visible, infrared, and ultraviolet can be used as acarrier for the transmission of data preferably using infrared light asthe carrier for the transmission system. An LED can be mounted in thecontact device and transmit modulated signals to remotely placedreceivers with the light emitted from the LED being modulated by thesignal. When using this embodiment, the contact device in the receiverunit has the following components: a built in infrared light emitter(950 mn), an infrared detector, decoder, display, and CPU. Prior totransmission, the physiologic variables found on the eye or tear fluidare multiplexed and encoded by pulse interval modulation, pulsefrequency modulation, or the like. The infrared transmitter then emitsshort duration pulses which are sensed by a remotely placed photodiodein the infrared detector which is subsequently decoded, processed, andrecorded. The light transmitted from the LED is received at the opticalreceiver and transformed into electrical signals with subsequentregeneration of the biosignals. Infrared light is reflected quite wellincluding surfaces that do not reflect visible light and can be used inthe transmission of physiological variables and position/motionmeasurement. This embodiment is particularly useful when there islimitations in bandwidth as in radio transmission. Furthermore, thisembodiment may be quite useful with closed eyes since the light can betransmitted through the skin of the eyelid.

It is also understood that the transmission of data from the contactdevice can be accomplished by the use of sound and ultrasound being thepreferred way of transmission underwater since sound is less stronglyattenuated by water than radio waves. The information is transmittedusing modulated sound signals with the sound waves being transmitted toa remote receiver. There is a relatively high absorption of ultrasonicenergy by living tissues, but since the eye even when closed has arather thin intervening tissue the frequency of the ultrasonic energy isnot restricted. However, soundwaves are not the preferred embodimentsince they can take different paths from their source to a receiver withmultiple reflections that can alter the final signal. Furthermore, it isdifficult to transmit rapidly changing biological variables because ofthe relatively low velocity of sound as compared to electromagneticradiation. It is possible though to easily mount an ultrasonicendoradiosonde in the contact device such as for transmitting pH valuesor temperature. An ultrasonic booster transmitter located nearby orcarried by the subject can be used to transmit the signal at a higherpower level. An acoustic tag with a magnetic compass sensor can be usedwith the information acoustically telemetered to a sector scanningsonar.

A preferred embodiment of the invention consists of electrodes, FMtransmitter, and a power supply mounted in the contact device. Stainlesssteel micro cables are used to connect the electronics to thetransducers to the battery power supply. A variety of amplifiers and FMtransmitters including Colpitts oscillator, crystal oscillators andother oscillators preferably utilizing a custom integrated circuitapproach with ultra density circuitry can be used in the apparatus ofthe invention.

Several variables can be simultaneously transmitted using differentfrequencies using several transmitters housed in the contact device.Alternatively, a single transmitter (3 channel transmitter) can transmitcombined voltages to a receiver, with the signal being subsequentlydecoded, separated into three parts, filtered and regenerated as thethree original voltages (different variables such as glucose level,pressure and temperature). A multiple channel system incorporating allsignal processing on a single integrated circuit minimizesinterconnections and can be preferably mounted in the apparatus of theinvention when multiple simultaneous signal transmission is needed suchas transmitting the level of glucose, temperature, bioelectrical, andpressure. A single-chip processor can be combined with a logic chip toalso form a multichannel system for the apparatus of the inventionallowing measurement of several parameters as well as activation oftransducers.

It is understood that a variety of passive, active, and inductive powersources can be used in the apparatus of the invention. The power supplymay consist of micro batteries, inductive power link, energy frombiological sources, nuclear cells, micro power units, fuel cells whichuse glucose and oxygen as energy sources, and the like. The type ofpower source is chosen according to the biological or biophysical eventto be transmitted.

A variety of signal receivers can be used such a frame aerial connectedto a conventional FM receiver from which the signal is amplified decodedand processed. Custom integrated circuits will provide the signalprocessing needed to evaluate the parameters transmitted such astemperature, pressure flow dimensions, bioelectrical activity,concentration of chemical species and the like. The micro transducers,signal processing electronics, transmitters and power source can bebuilt in the contact device.

Power for the system may be supplied from a power cell activated by amicropower control switch contained in the contact device or can beremotely activated by radio frequency means, magnetic means and thelike. Inductive radio frequency powered telemetry in which the same coilsystem used to transfer energy is used for the transmission of datasignal can be used in the apparatus of the invention. The size of thesystem relates primarily to the size of the batteries and thetransmitter. The size of conventional telemetry systems are proportionalto the size of the batteries because most of the volume is occupied bybatteries. The size of the transmitter is related to the operatingfrequency with low frequencies requiring larger components than higherfrequency circuits. Radiation at high frequencies are more attenuatedthan lower frequencies by body tissues. Thus a variety of systemsimplanted inside the body requires lower frequency devices andconsequently larger size components in order for the signal to be lessatenuated. Since the apparatus of the invention is placed on the surfaceof the eye there is little to no attenuation of signals and thus higherfrequency small devices can be used. Furthermore, very small batteriescan be used since the contact device can be easily retrieved and easilyreplaced. The large volume occupied by batteries and power sources inconventional radio telemetry implantable devices can be extremelyreduced since the apparatus of the invention is placed externally on theeye and is of easy access and retrieval, and thus a very small batterycan be utilized and replaced whenever needed.

A variety of system assemblies can be used but the densest systemassembly is preferred such as a hybrid assembly of custom integratedcircuits which permits realization of the signal processing needed forthe applications. The typical resolution of such circuits are in theorder of a few microns and can be easily mounted in the contact device.A variety of parameters can be measured with one integrated circuitwhich translates the signals preferably into a transmission bandwidth.Furthermore, a variety of additional electronics and a complementarymetal oxide semiconductor (CMOS) chip can be mounted in the apparatus ofthe invention for further signal processing and transmission.

The micropower integrated circuits can be utilized with a variety oftransmitter modalities mounted in the intelligent contact lens includingradio links, ultrasonic link and the like. A variety of other integratedcircuits can be mounted in the contact device such as signal processorsfor pressure and temperature, power switches for external control ofimplanted electronics and the like. Pressure transducers such as acapacitive pressure transducer with integral electronics for signalprocessing can be incorporated in the same silicon structure and can bemounted in the contact device. Evolving semiconductor technology andmore sophisticated encoding methods as well as microminiature integratedcircuits amplifiers and receivers are expected to occur and can behoused in the contact device. It is understood that a variety oftransmitters, receivers, and antennas for transmitting and receivingsignals in telemetry can be used in the apparatus of the invention, andhoused in the contact device and/or placed remotely for receiving,processing, and analyzing the signal.

The fluid present on the front surface of the eye covering theconjunctiva and cornea is referred as the tear film or tear fluid. Closeto 100% of the tear film is produced by the lacrimal gland and secretedat a rate of 2 μl/min. The volume of the tear fluid is approximately 10μl. The layer of tear fluid covering the cornea is about 8-10 μm inthickness and the tear fluid covering the conjunctiva is about 1 5 μmthick. The pre-corneal tear film consists of three layers: a thin lipidlayer measuring about 0.1 μm consisting of the air tear interface, amucin layer measuring 0.03μm which is in direct contact with the cornealepithelium, and finally the remaining layer is the thick aqueous layerwhich is located between the lipid and mucin layer. The aqueous layer isprimarily derived from the secretions of the lacrimal gland and itschemical composition is very similar to diluted blood with a reducedprotein content and slightly greater osmotic pressure. The secretion andflow of tear fluid from the lacrimal gland located in thesupero-temporal quadrant with the subsequent exit through the lacrimalpuncta located in the infero-medial quadrant creates a continuous flowof tear fluid providing the ideal situation by furnishing a continuoussupply of substrate for one of the stoichiometric reactions which is thesubject of a preferred embodiment for evaluation of glucose levels. Themain component of the tear fluid is the aqueous layer which is anultrafiltrate of blood containing electrolytes such as sodium,potassium, chloride, bicarbonate, calcium, and magnesium as well asamino acids, proteins, enzymes, DNA, lipids, cholesterol, glycoproteins,immunoglobulins, vitamins, minerals and hormones. Moreover, the aqueouslayer also holds critical metabolites such as glucose, urea,catecholainines, and lactate, as well as gases such as oxygen and carbondioxide. Furthermore, any exogenous substances found in the blood streamsuch as drugs, radioactive compounds and the like are present in thetear fluid. Any compound present in the blood can potentiallynoninvasively be evaluated with the apparatus of the invention with thedata transmitted and processed at a remotely located station.

According to one preferred embodiment of the invention, the non-invasiveanalysis of glucose levels will be described: Glucose Detection:--Theapparatus and methods for measurement of blood components and chemicalspecies in the tear fluid and/or surface of the eye is based onelectrodes associated with enzymatic reactions providing an electricalcurrent which can be radio transmitted to a remote receiver providingcontinuous data on the concentration of species in the tear fluid orsurface of the eye. The ICL system is preferably based on a diffusionlimited sensors method that requires no reagents or mechanical/movingparts in the contact device. The preferred method and apparatus of theglucose detector using ICL uses the enzyme glucose oxidase whichcatalyze a reaction involving glucose and oxygen in association withelectrochemical sensors mounted in the contact device that are sensitiveto either the product of the reaction, an endogenous coreactant, or acoupled electron carrier molecule such as the ferrocene-mediated glucosesensors, as well as the direct electrochemical reaction of glucose atthe contact device membrane-covered catalytic metal electrode.

Glucose and oxygen present in the tear fluid either derived from thelacrimal gland or diffused from vessels on the surface of the eye willdiffuse into the contact device reaching an immobilized layer of enzymeglucose oxidase mounted in the contact device. Successful operation ofenzyme electrodes demand constant transport of the substrate to theelectrode since the substrate such as glucose and oxygen are consumedenzymatically. The ICL is the ideal device for using enzyme electrodessince the tear fluid flows continuously on the surface of the eyecreating an optimal environment for providing substrate for thestoichiometric reaction. The ICL besides being a noninvasive systemsolves the critical problem of sensor lifetime which occurs with anysensors that are implanted inside the body. The preferred embodimentrefers to amperometric glucose biosensors with the biosensors based onbiocatalytic oxidation of glucose in the presence of the enzyme oxidase.This is a two step process consisting of enzymatic oxidation of glucoseby glucose oxidase in which the co-factor flavin-adenine dinucleotide(FAD) is reduced to FADH₂ followed by oxidation of the enzyme co-factorby molecular oxygen with formation of hydrogen peroxide. ##STR1##

    H.sub.2 O.sub.2 →1/2O.sub.2 +H.sub.2 O

With catalase enzyme the overall reaction is

    glucose+1/2O.sup.2 →gluconic acid

Glucose concentration can be measured either by electrochemicaldetection of an increase of the anodic current due to hydrogen peroxide(product of the reaction) oxidation or by detection of the decrease inthe cathodic current due to oxygen (co-reactant) reduction. The ICLglucose detection system preferably has an enzyme electrode in contactwith the tear fluid and/or surface of the eye capable of measuring theoxidation current of hydrogen peroxide created by the stoichiometricconversion of glucose and oxygen in a layer of glucose oxidase mountedinside the contact device. The ICL glucose sensor is preferablyelectrochemical in nature and based on a hydrogen peroxide electrodewhich is converted by immobilized glucose oxidase which generates adirect current depending on the glucose concentration of the tear fluid.

The glucose enzyme electrode of the contact device responds to changesin the concentration of both glucose and oxygen, both of which aresubstrates of the immobilized enzyme glucose oxidase. It is alsounderstood that the sensor in the contact device can be made responsiveto glucose only by operating in a differential mode. The enzymaticelectrodes built in the contact device are placed in contact with thetear fluid or the surface of the eye and the current generated by theelectrodes according to the stoichiometric conversion of glucose, aresubsequently converted to a frequency audio signal and transmitted to aremote receiver, with the current being proportional to the glucoseconcentration according to calibration factors.

The signals can be transmitted using the various transmission systemspreviously described with an externally placed receiver demodulating theaudio frequency signal to a voltage and the glucose concentration beingcalculated from the voltage and subsequently displayed on a LED display.An interface card can be used to connect the receiver with a computerfor further signal processing and analysis. During oxidation of glucoseby glucose oxidase an electrochemically oxidable molecule or any otheroxidable species generated such as hydrogen peroxide can be detectedamperometrically as a current by the electrodes. A preferred embodimentincludes a tree electrode setup consisting of a working electrode(anode) and auxiliary electrode (cathode) and a reference electrodeconnected to an amperometric detector. It should be noted though, that aglucose sensor could function well using two electrodes. Whenappropriate voltage difference is applied between the working andauxiliary electrode, hydrogen peroxide is oxidized on the surface of theworking electrode which creates a measurable electric current. Theintensity of the current generated by the sensor is proportional to theconcentration of hydrogen peroxide which is proportional to theconcentration of glucose in the tear film and the surface of the eye.

A variety of materials can be used for the electrodes such assilver/silver chloride coded cathodes. Anodes may be preferablyconstructed as a platinum wire coated with glucose oxidase or preferablycovered by a immobilized glucose oxidase membrane. Several possibleconfigurations for sensors using amperometric enzyme electrodes whichinvolves detection of oxidable species can be used in the apparatus ofthe invention. A variety of electrodes and setups can be used in thecontact device which are capable of creating a stable working potentialand output current which is proportional to the concentration of bloodcomponents in the tear fluid and surface of the eye. It is understoodthat a variety of electrode setups for the amperometric detection ofoxidable species can be accomplished with the apparatus of theinvention. It is understood that solutions can be applied to the surfaceof the electrodes to enhance transmission.

Other methods which use organic mediators such as ferrocene whichtransfers electrons from glucose oxidase to a base electrode withsubsequent generation of current can be utilized. It is also understoodthat needle-type glucose sensors can be placed in direct contact withthe conjunctiva or encased in a contact device for measurement ofglucose in the tear fluid. It is understood that any sensor capable ofconverting a biological variable to a voltage signal can be used in thecontact device and placed on the surface of the eye for measurement ofthe biological variables. It is understood that any electrodeconfiguration which measures hydrogen peroxide produced in the reactioncatalysed by glucose oxidase can be used in the contact device formeasurement of glucose levels. It is understood that the followingoxygen based enzyme electrode glucose sensor can be used in theapparatus of the invention which is based on the principal that theoxygen not consumed by the enzymatic reactions by catalase enzyme iselectrochemically reduced at an oxygen sensor producing a glucosemodulated oxygen dependent current. This current is compared to acurrent from a similar oxygen sensor without enzymes.

It is understood that the sensors are positioned in a way to optimizethe glucose access to the electrodes such as by creating micro traumasto increase diffusion of glucose across tissues and capillary walls,preferably positioning the sensors against vascularized areas of theeye. In the closed eye about two-thirds of oxygen and glucose comes bydiffusion from the capillaries. Thus positioning the sensors against thepalpebral conjunctiva during blinking can increase the delivery ofsubstrates to the contact device biosensor allowing a useful amount ofsubstrates to diffuse through the contact device biosensor membranes.

There are several locations on the surface of the eye in which the ICLcan be used to measure glucose such as: the tear film laying on thesurface of the cornea which is an ultrafiltrate of blood derived fromthe main lacrimal gland; the tear meniscus which is a reservoir of tearson the edge of the eye lid; the supero-temporal conjunctival fornixwhich allows direct measurement of tears at the origin of secretion; thelimbal area which is a highly vascularized area between cornea and thesclera; and preferably the highly vascularized conjunctiva. The contactdevice allows the most efficient way of acquiring fluid by creatingmicro-damage to the epithelium with a consequent loss of the bloodbarrier function of said epithelium, with the subsequent increase intissue fluid diffusion. Furthermore, mechanical irritation caused by anintentionally constructed slightly rugged surface of the contact devicein order to increase the flow of substrates. Furthermore, it isunderstood that a heating element can be mounted in association with thesensor in order to increase transudation of fluid.

The samples utilized for noninvasive blood analysis may preferably beacquired by micro-traumas to the conjunctiva caused by the contactdevice which has micro projections on its surface in contact with theconjunctiva creating an increase in the diffusion rate of plasmacomponents through the capillary walls toward the measuring sensors.Moreover, the apparatus of the invention may promote increased vascularpermeability of conjunctival vessels through an increase in temperatureusing surface electrodes as heating elements. Furthermore, the sensorsmay be located next to the exit point of the lacrimal gland duct inorder to collect tear fluid close to its origin. Furthermore, thesensors may be placed inferiorly in contact with the conjunctival tearmeniscus which has the largest volume of tear fluid on the surface ofthe eye. Alternatively, the sensors may be placed in contact with thelimbal area which is a substantially vascularized surface of the eye.Any means that create a micro-disruption of the integrity of the ocularsurface or any other means that cause transudation of tissue fluid andconsequently plasma may be used in the invention. Alternatively, thesensors may be placed against the vascularized conjunctiva in thecul-de-sac superiorly or inferiorly.

It is also understood that the sensors can be placed on any location onthe surface of the eye to measure glucose and other chemical compounds.Besides the conventional circular shape of contact lenses, the shape ofthe contact device also includes a flat rectangular configuration, ringlike or half moon like which are used for applications that requireplacement under the palpebral conjunctiva or cul-de-sac of the eye.

A recessed region is created in the contact device for placement of theelectrodes and electronics with enzyme active membranes placed over theelectrodes. A variety of membranes with different permeabilities todifferent chemical species are fitted over the electrodes andenzyme-active membranes. The different permeability of the membranesallows selection of different chemicals to be evaluated and to preventcontaminants from reaching the electrodes. Thus allowing severalelectroactive compounds to be simultaneously evaluated by mountingmembranes with different permeabilities with suitable electrodes on thecontact device.

It is also understood that multilayer membranes with preferentialpermeability to different compounds can be used. The contact deviceencases the microelectrodes forming a bioprotective membrane such thatthe electrodes are covered by the enzyme active membrane which iscovered by the contact device membrane such as polyurethane which isbiocompatable and permeable to the analytes A membrane between theelectrodes and the enzyme membrane can be used to block interferingsubstances without altering transport of peroxide ion. The permeabilityof the membranes are used to optimize the concentration of the compoundsneeded for the enzymatic reaction and to protect against interferingelements.

It is understood that the diffusion of substrate to the sensor mountedin the contact device is preferably perpendicular to the plane of theelectrode surface. Alternatively, it is understood that the membrane andsurface of the contact device can be constructed to allow selectivenon-perpendicular diffusion of the substrates. It is also understoodthat membranes such as negatively charged perfluorinated ionomer Nafionmembrane can be used in order to reduce interference by electroactivecompounds such as ascorbate, urate and acetaminophen. It is alsounderstood that new polymers and coatings under development which arecapable of preferential selection of electroactive compounds and thatcan prevent degradation of electrodes and enzymes can be used in theapparatus of the invention.

The sensors and membranes coupled with radio transmitters can bepositioned in any place in the contact device but may be placed in thecardinal positions in a pie like configuration, with each sensortransmitting its signal to a receiver. For example, if four biologicalvariables are being detected simultaneously the four sensors signals A,B, C, and D are simultaneously transmitted to one or more receivers. Anydevice utilizing the tear fluid to non-invasively measure the bloodcomponents and signals transmitted to a remote station can be used inthe apparatus of the invention. Preferably a small contact device,however any size or shape of contact devices can be used to acquire thedata on the surface of the eye.

An infusion pump can be activated according to the level of glucosedetected by the ICL system and insulin injected automatically as neededto normalize glucose levels as an artificial pancreas. An alarm circuitcan also be coupled with the pump and activated when low or high levelsof glucose are present thus alerting the patient. It is understood thatother drugs, hormones, and chemicals can be detected and signalstransmitted in the same fashion using the apparatus of the invention.

A passive transmitter carrying a resonance circuit can be mounted in thecontact device with its frequency altered by a change in reactance whosemagnitude changes in response to the voltage generated by the glucosesensors. As the signal from passive transmitters falls off extremelyrapidly with distance, the antenna and receiver should be placed near tothe contact device such as in the frame of regular glasses.

It is also understood that active transmitters with batteries housed inthe contact device and suitable sensors as previously described can alsobe used to detect glucose levels. It is also understood that a vibratingmicro-quartz crystal connected to a coil and capable of sending bothsound and radio impulses can be mounted in the contact device andcontinuously transmit data signals related to the concentration ofchemical compounds in the tear fluid.

An oxygen electrode consisting of a platinum cathode and a silver anodeloaded with polarographic voltage can be used in association with theglucose sensor with the radio transmission of the two variables. It isalso understood that sensors which measure oxygen consumption asindirect means of evaluating glucose levels can be used in the apparatusof the invention. The membranes can be used to increase the amount ofoxygen delivered to the membrane enzyme since all glucose oxidasesystems require oxygen and can potentially become oxygen limited. Themembranes also can be made impermeable to other electroactive speciessuch as acetamymophen or substances that can alter the level of hydrogenperoxide produced by the glucose oxidase enzyme membrane.

It is understood that a polarographic Clark-type oxygen detectorelectrode consisting of a platinum cathode in asilver-to-silver-chloride anode with signals telemetered to a remotestation can be used in the apparatus of the invention. It is alsounderstood that other gas sensors using galvanic configuration and thelike can be used with the apparatus of the invention. The oxygen sensoris preferably positioned so as to lodge against the palpebralconjunctiva. The oxygen diffusing across the electrode membrane isreduced at the cathode which produces a electrical current which isconverted to an audio frequency signal and transmitted to a remotestation. The placement of the sensor in the conjunctiva allows intimatecontact with an area vascularized by the same arterial circulation asthe brain which correlates with arterial oxygen and provides anindication of peripheral tissue oxygen. This embodiment allows goodcorrelation between arterial oxygen and cerebral blood flow bymonitoring a tissue bed vascularized by the internal carotid artery, andthus, reflects intracranial oxygenation.

This embodiment can be useful during surgical procedures such as incarotid endarterectomy allowing precise detection of the side withdecreased oxygenation. This same embodiment can be useful in a varietyof heart and brain operations as well as in retinopathy of prematuritywhich allows close observation of the level of oxygen administered andthus prevention of hyperoxia with its potentially blinding effects whilestill delivering adequate amount of oxygen to the infant.

Cholesterol secreted in the tear fluid correlates with plasmacholesterol and a further embodiment utilizes a similar system asdescribed by measurement of glucose. However, this ICL as designed bythe inventor involves an immobilized cholesterol esterase membrane whichsplits cholesterol esters into free cholesterol and fatty acids. Thefree cholesterol passes through selectively permeable membrane to bothfree cholesterol and oxygen and reaches a second membrane consisting ofan immobilized cholesterol oxidase. In the presence of oxygen the freecholesterol is transformed by the cholesterol oxidase into cholestenoneand hydrogen peroxide with the hydrogen peroxide being oxidized on thesurface of the working electrode which creates a measurable electriccurrent with signals preferably converted into audio frequency signalsand transmitted to a remote receiver with the current being proportionalto the cholesterol concentration according to calibration factors. Themethod and apparatus described above relates to the following reactionor part of the following reaction. Cholesterol ester cholesterolesterase→Free cholesterol+fatty acids Free cholesterol+O₂ cholesteroloxidase→Cholestenone+H₂ O₂

A further embodiment utilizes an antimone electrode that can be housedin the contact device and used to detect the pH and other chemicalspecies of the tear fluid and the surface of the eye. It is alsounderstood that a glass electrode with a transistor circuit capable ofmeasuring pH, pH endoradiosondes, and the like can be used and mountedin the contact device and used for measurement of the pH in the tearfluid or surface of the eye with signals preferably radio transmitted toa remote station.

In another embodiment, catalytic antibodies immobilized in a membranewith associated pH sensitive electrodes can identify a variety ofantigens. The antigen when interacting with the catalytic antibody canpromote the formation of acetic acid with a consequent change in pH andcurrent that is proportional to the concentration of the antigensaccording to calibration factors.

In a further embodiment an immobilized electrocatalytic active enzymeand associated electrode promote, in the presence of a substrate(meaning any biological variable), an electrocatalytic reactionresulting in a current that is proportional to the amount of saidsubstrate. It is understood that a variety of enzymatic and nonenzymaticdetection systems can be used in the apparatus of the invention.

It is understood that any electrochemical sensor, thermoelectricsensors, acoustic sensors, piezoelectric sensors, optical sensors, andthe like can be mounted in the contact device and placed on the surfaceof the eye for detection and measurement of blood components andphysical parameters found in the eye with signals preferably transmittedto a remote station. It is understood that electrochemical sensors usingamperometric, potentiometric, conductometric, gravimetric, impedimetric,systems, and the like can be used in the apparatus of the invention fordetection and measurement of blood components and physical parametersfound in the eye with signals preferably transmitted to a remotestation.

Some preferable ways have been described; however, any other miniatureradio transmitters can be used and mounted in the contact device and anymicrominiature sensor that modulates a radio transmitter and send thesignal to a nearby radio receiver can be used. Other microminiaturedevices capable of modulating an ultrasound device, or infrared andlaser emitters, and the like can be mounted in the contact device andused for signal detection and transmission to a remote station. Avariety of methods and techniques and devices for gaining andtransmitting information from the eye to a remote receiver can be usedin the apparatus of the invention.

It is an object of the present invention to provide an apparatus andmethod for the non-invasive measurement and evaluation of bloodcomponents.

It is also an object of the present invention to provide an intelligentcontact lens system capable of receiving, processing, and transmittingsignals such as electromagnetic waves, radio waves, infrared and thelike being preferably transmitted to a remote station for signalprocessing and analysis, with transensors and biosensors mounted in thecontact device.

It is a further object of the present invention to detect physicalchanges that occur in the eye, preferably using optical emitters andsensors.

It is a further object of the present invention to provide a novel drugdelivery system and treatment of eye and systemic diseases.

The above and other objects and advantages will become more readilyapparent when reference is made to the following description taken inconjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic block diagram illustrating a system for measuringintraocular pressure in accordance with a preferred embodiment of thepresent invention.

FIGS. 2A-2D schematically illustrate a preferred embodiment of a contactdevice according the present invention.

FIG. 3 schematically illustrates a view seen by a patient when utilizingthe system illustrated in FIG. 1.

FIGS. 4 and 5 schematically depict multi-filter optical elements inaccordance with a preferred embodiment of the present invention.

FIGS. 5A-5F illustrate a preferred embodiment of an applicator forgently applying the contact device to the cornea in accordance with thepresent invention. FIG. 6 illustrates an exemplary circuit for carryingout several aspects of the embodiment illustrated in FIG. 1.

FIGS. 7A and 7B are block diagrams illustrating an arrangement capablecompensating for deviations in corneal thickness according to thepresent invention.

FIGS. 8A and 8B schematically illustrate a contact device utilizingbarcode technology in accordance with a preferred embodiment of thepresent invention.

FIGS. 9A and 9B schematically illustrate a contact device utilizingcolor detection technology in accordance with a preferred embodiment ofthe present invention.

FIG. 10 illustrates an alternative contact device in accordance with yetanother preferred embodiment of the present invention.

FIGS. 11A and 11B schematically illustrate an indentation distancedetection arrangement in accordance with a preferred embodiment of thepresent invention.

FIG. 12 is a cross-sectional view of an alternative contact device inaccordance with another preferred embodiment of the present invention.

FIG. 13A is a cross-sectional view of an alternative contact device.

FIG. 13B is a cross-sectional view of an alternative contact device.

FIG. 14 is a cross-sectional view of an alternative contact device.

FIG. 15 is a cross-sectional view of an alternative contact device.

FIG. 16 schematically illustrates an alternative embodiment of thesystem for measuring intraocular pressure by applanation, according tothe present invention.

FIG. 16A is a graph depicting force (F) as a function of the distance(x) separating a movable central piece from the pole of a magneticactuation apparatus in accordance with the present invention.

FIG. 17 schematically illustrates an alternative optical alignmentsystem in accordance with the present invention.

FIGS. 18 and 19 schematically illustrate arrangements for guiding thepatient during alignment of his/her eye in the apparatus of the presentinvention.

FIGS. 20A and 20B schematically illustrate an alternative embodiment formeasuring intraocular pressure by indentation.

FIGS. 21 and 22 schematically illustrate embodiments of the presentinvention which facilitate placement of the contact device on the scleraof the eye.

FIG. 23 is a plan view of an alternative contact device which may beused to measure episcleral venous pressure in accordance with thepresent invention.

FIG. 24 is a cross-sectional view of the alternative contact devicewhich may be used to measure episcleral venous pressure in accordancewith the present invention.

FIG. 25 schematically illustrates an alternative embodiment of thepresent invention, which includes a contact device with a pressuretransducer mounted therein.

FIG. 25A is a cross-sectional view of the alternative embodimentillustrated in FIG. 25.

FIG. 26 is a cross-sectional view illustrating the pressure transducerof FIG. 25.

FIG. 27 schematically illustrates the alternative embodiment of FIG. 25when located in a patient's eye.

FIG. 28 illustrates an alternative embodiment wherein two pressuretransducers are utilized.

FIG. 29 illustrates an alternative embodiment utilizing a centrallydisposed pressure transducer.

FIG. 30 illustrates a preferred mounting of the alternative embodimentto eye glass frames.

FIG. 31 is a block diagram of a preferred circuit defined by thealternative embodiment illustrated in FIG. 25.

FIG. 32 is a schematic representation of a contact device situated onthe cornea of an eye with lateral extensions of the contact deviceextending into the sclera sack below the upper and lower eye lids andillustrating schematically the reception of a signal transmitted from atransmitter to a receiver and the processes performed on the transmittedsignal.

FIG. 33A is an enlarged view of the contact device shown in FIG. 32 withfurther enlarged portions of the contact device encircled in FIG. 33Abeing shown in further detail in FIGS. 33B and 33C.

FIG. 34 is a schematic block diagram of a system of obtaining samplesignal measurements and transmitting and interpreting the results of thesample signals.

FIGS. 35A and 35C schematically represent the actuation of the contactdevice of the present invention by the opening and closing of the eyelids. FIG. 35B is an enlarged detail view of an area encircled in FIG.35A.

FIGS. 36A through 36J schematically illustrate various shapes of acontact device incorporating the principles of the present invention.

FIGS. 37A and 37B schematically illustrate interpretation of signalsgenerated from the contact device of the present invention and theanalysis of the signals to provide different test measurements andtransmission of this data to remote locations, such as an intensive careunit setting.

FIG. 38A schematically illustrates a contact device of the presentinvention with FIG. 38B being a sectional view taken along the sectionline shown in FIG. 38A.

FIG. 39A illustrates the continuous flow of fluid in the eye. FIG. 39Bschematically illustrates an alternative embodiment of the contactdevice of the present invention used under the eyelid to produce signalsbased upon flow of tear fluid through the eye and transmit the signalsby a wire connected to an external device.

FIG. 40A schematically illustrates an alternative embodiment of thepresent invention, used under the eye lid to produce signals indicativeof sensed glucose levels which are radio transmitted to a remote stationfollowed by communication through a publically available network.

FIG. 40B schematically illustrates an alternative embodiment of theglucose sensor to be used under the eyelid with signals transmittedthrough wires.

FIG. 41 illustrates an oversized contact device including a plurality ofsensors.

FIG. 42A illustrates open eye lids positioned over a contact deviceincluding a somnolence awareness device, whereas FIG. 42B illustratesthe closing of the eyelids and the production of a signal externallytransmitted to an alarm device.

FIG. 43 is a detailed view of a portion of an eyeball including a heatstimulation transmission device.

FIG. 44 is a front view of a heat stimulation transmission devicemounted on a contact device and activated by a remote hardware device.

FIG. 45 illustrates a band heat stimulation transmission device forexternal use or surgical implantation in any part of the body.

FIG. 46 illustrates a surgically implantable heat stimulationtransmission device for implantation in the eye between eye muscles.

FIG. 47 illustrates a heat stimulation device for surgical implantationin any part of the body.

FIG. 48 schematically illustrates the surgical implantation of anoverheating transmission device adjacent to a brain tumor.

FIG. 49 illustrates the surgical implantation of an overheatingtransmission device adjacent to a kidney tumor.

FIG. 50 illustrates an overheating transmission device and its variouscomponents.

FIG. 51 illustrates the surgical implantation of an overheatingtransmission devices adjacent to an intraocular tumor.

FIG. 52 schematically illustrates the surgical implantation of anoverheating transmission device adjacent to a lung tumor.

FIG. 53 schematically illustrates the positioning of an overheatingtransmission device adjacent to a breast tumor.

FIG. 54A is a side sectional view and FIG. 54B is a front view of acontact device used to detect chemical compounds in the aqueous humorlocated on the eye, with FIG. 54C being a side view thereof.

FIG. 55A schematically illustrates a microphone or motion sensor mountedon a contact device sensor positioned over the eye for detection ofheart pulsations or sound and transmission of a signal representative ofheart pulsations or sound to a remote alarm device with FIG. 55B beingan enlarged view of the alarm device encircled in FIG. 55A.

FIG. 56 illustrates a contact device with an ultrasonic dipolar sensor,power source and transmitter with the sensor located on the bloodvessels of the eye.

FIG. 57 schematically illustrates the location of a contact device witha sensor placed near an extraocular muscle.

FIG. 58A is a side sectional view illustrating a contact device having alight source for illumination of the back of the eye. FIG. 58Billustrates schematically the transmission of light from a light sourcefor reflection off a blood vessel at the cup of the optic nerve and forreceipt of the reflected light by a multioptical filter system separatedfrom the reflecting surface by a predetermined distance and separatedfrom the light source by a predetermined distance for interpretation ofthe measurement of the reflected light.

FIGS. 59A through 59C illustrate positioning of contact devices forneurostimulation of tissues in the eye and brain.

FIG. 60 is a schematic illustration of a contact device having a fixedfrequency transmitter and power source for being tracked by an orbitingsatellite.

FIG. 61 illustrates a contact device under an eyelid including apressure sensor incorporated in a circuit having a power source, an LEDdrive and an LED for production of an LED signal for remote activationof a device having a photodiode or optical receiver on a receptorscreen.

FIG. 62 is a cross-sectional view of a contact device having a drugdelivery system incorporated therein.

FIG. 63 schematically illustrates a block diagram of an artificialpancreas system.

DESCRIPTION OF THE PREFERRED EMBODIMENTS APPLANATION

A preferred embodiment of the present invention will now be describedwith reference to the drawings. According to the preferred embodimentillustrated in FIG. 1, a system is provided for measuring intraocularpressure by applanation. The system includes a contact device 2 forplacement in contact with the cornea 4, and an actuation apparatus 6 foractuating the contact device 2 so that a portion thereof projectsinwardly against the cornea 4 to provide a predetermined amount ofapplanation. The system further includes a detecting arrangement 8 fordetecting when the predetermined amount of applanation of the cornea 4has been achieved and a calculation unit 10 responsive to the detectingarrangement 8 for determining intraocular pressure based on the amountof force the contact device 2 must apply against the cornea 4 in orderto achieve the predetermined amount of applanation.

The contact device 2 illustrated in FIG. 1 has an exaggerated thicknessto more clearly distinguish it from the cornea 4. FIGS. 2A-2D moreaccurately illustrate a preferred embodiment of the contact device 2which includes a substantially rigid annular member 12, a flexiblemembrane 14 and a movable central piece 16. The substantially rigidannular member 12 includes an inner concave surface 18 shaped to matchan outer surface of the cornea 4 and having a hole 20 defined therein.The substantially rigid annular member 12 has a maximum thickness(preferably approximately 1 millimeter) at the hole 20 and aprogressively decreasing thickness toward a periphery 21 of thesubstantially rigid annular member 12. The diameter of the rigid annularmember is approximately 11 millimeters and the diameter of the hole 20is approximately 5.1 millimeters according to a preferred embodiment.Preferably, the substantially rigid annular member 12 is made oftransparent polymethylmethacrylate; however, it is understood that manyother materials, such as glass and appropriately rigid plastics andpolymers, may be used to make the annular member 12. Preferably, thematerials are chosen so as not to interfere with light directed at thecornea or reflected back therefrom.

The flexible membrane 14 is preferably secured to the inner concavesurface 18 of the substantially rigid annular member 12 to providecomfort for the wearer by preventing scratches or abrasions to thecorneal epithelial layer. The flexible membrane 14 is coextensive withat least the hole 20 in the annular member 12 and includes at least onetransparent area 22. Preferably, the transparent area 22 spans theentire flexible membrane 14, and the flexible membrane 14 is coextensivewith the entire inner concave surface 18 of the rigid annular member 12.According to a preferred arrangement, only the periphery of the flexiblemembrane 14 and the periphery of the rigid annular member 12 are securedto one another. This tends to minimize any resistance the flexiblemembrane might exert against displacement of the movable central piece16 toward the cornea 4.

According to an alternative arrangement, the flexible membrane 14 iscoextensive with the rigid annular member and is heat-sealed theretoover its entire extent except for a circular region within approximatelyone millimeter of the hole 20.

Although the flexible membrane 14 preferably consists of a soft and thinpolymer, such as transparent silicone elastic, transparent siliconrubber (used in conventional contact lens), transparent flexible acrylic(used in conventional intraocular lenses), transparent hydrogel, or thelike, it is well understood that other materials may be used inmanufacturing the flexible membrane 14.

The movable central piece 16 is slidably disposed within the hole 20 andincludes a substantially flat inner side 24 secured to the flexiblemembrane 14. The engagement of the inner side 24 to the flexiblemembrane 14 is preferably provided by glue or thermo-contact techniques.It is understood, however, that various other techniques may be used inorder to securely engage the inner side 24 to the flexible membrane 14.Preferably, the movable central piece 16 has a diameter of approximately5.0 millimeters and a thickness of approximately 1 millimeter.

A substantially cylindrical wall 42 is defined circumferentially aroundthe hole 20 by virtue of the increased thickness of the rigid annularmember 12 at the periphery of the hole 20. The movable central piece 16is slidably disposed against this wall 42 in a piston-like manner andpreferably has a thickness which matches the height of the cylindricalwall 42. In use, the substantially flat inner side 24 flattens a portionof the cornea 4 upon actuation of the movable central piece 16 by theactuation apparatus 6.

The overall dimensions of the substantially rigid annular member 12, theflexible membrane 14 and the movable central piece 16 are determined bybalancing several factors, including the desired range of forces appliedto the cornea 4 during applanation, the discomfort tolerances of thepatients, the minimum desired area of applanation, and the requisitestability of the contact device 2 on the cornea 4. In addition, thedimensions of the movable central piece 16 are preferably selected sothat relative rotation between the movable central piece 16 and thesubstantially rigid annular member 12 is precluded, without hamperingthe aforementioned piston-like sliding.

The materials used to manufacture the contact device 2 are preferablyselected so as to minimize any interference with light incident upon thecornea 4 or reflected thereby.

Preferably, the actuation apparatus 6 illustrated in FIG. 1 actuates themovable central piece 16 to cause sliding of the movable central piece16 in the piston-like manner toward the cornea 4. In doing so, themovable central piece 16 and a central portion of the flexible membrane14 are caused to project inwardly against the cornea 4. This is shown inFIGS. 2C and 2D. A portion of the cornea 4 is thereby flattened.Actuation continues until a predetermined amount of applanation isachieved.

Preferably, the movable central piece 16 includes a magneticallyresponsive element 26 arranged so as to slide along with the movablecentral piece 16 in response to a magnetic field, and the actuationapparatus 6 includes a mechanism 28 for applying a magnetic fieldthereto. Although it is understood that the mechanism 28 for applyingthe magnetic field may include a selectively positioned bar magnet,according to a preferred embodiment, the mechanism 28 for applying themagnetic field includes a coil 30 of long wire wound in a closely packedhelix and circuitry 32 for producing an electrical current through thecoil 30 in a progressively increasing manner. By progressivelyincreasing the current, the magnetic field is progressively increased.The magnetic repulsion between the actuation apparatus 6 and the movablecentral piece 16 therefore increases progressively, and this, in turn,causes a progressively greater force to be applied against the cornea 4until the predetermined amount of applanation is achieved.

Using known principles of physics, it is understood that the electricalcurrent passing through the coil 30 will be proportional to the amountof force applied by the movable central piece 16 against the cornea 4via the flexible membrane 14. Since the amount of force required toachieve the predetermined amount of applanation is proportional tointraocular pressure, the amount of current required to achieve thepredetermined amount of applanation will also be proportional to theintraocular pressure. Thus, a conversion factor for converting a valueof current to a value of intraocular pressure can easily be determinedexperimentally upon dimensions of the system, the magneticresponsiveness of the magnetically responsive element 26, number of coilwindings, and the like.

Besides using experimentation techniques, the conversion factor may alsobe determined using known techniques for calibrating a tonometer. Suchknown techniques are based on a known relationship which exists betweenthe inward displacement of an indentation device and the volume changesand pressure in the indented eye. Examples of such techniques are setforth in Shiotz, Communications: Tonometry, The Brit. J. ofOphthalmology, June 1920, p. 249-266; Friedenwald, TonometerCalibration, Trans. Amer. Acad. of O. & O., January-February 1957, pp.108-126; and Moses, Theory and Calibration of the Schiotz Tonometer VII:Experimental Results of Tonometric Measurements: Scale Reading VersusIndentation Volume, Investigative Ophthalmology, September 1971, Vol.10, No. 9, pp. 716-723.

In light of the relationship between current and intraocular pressure,the calculation unit 10 includes a memory 33 for storing a current valueindicative of the amount of current passing through the coil 30 when thepredetermined amount of applanation is achieved. The calculation unit 10also includes a conversion unit 34 for converting the current value intoan indication of intraocular pressure.

Preferably, the calculation unit 10 is responsive to the detectingarrangement 8 so that when the predetermined amount of applanation isachieved, the current value (corresponding to the amount of currentflowing through the coil 30) is immediately stored in the memory 33. Atthe same time, the calculation unit 10 produces an output signaldirecting the current producing circuitry 32 to terminate the flow ofcurrent. This, in turn, terminates the force against the cornea 4. In analternative embodiment, the current producing circuitry 32 could be madedirectly responsive to the detecting arrangement 8 (i.e., not throughthe calculation unit 10) so as to automatically terminate the flow ofcurrent through the coil 30 upon achieving the predetermined amount ofapplanation.

The current producing circuitry 32 may constitute any appropriatelyarranged circuit for achieving the progressively increasing current.However, a preferred current producing circuit 32 includes a switch anda DC power supply, the combination of which is capable of producing astep function. The preferred current producing circuitry 32 furthercomprises an integrating amplifier which integrates the step function toproduce the progressively increasing current.

The magnetically responsive element 26 is circumferentially surroundedby a transparent peripheral portion 36. The transparent peripheralportion 36 is aligned with the transparent area 22 and permits light topass through the contact device 2 to the cornea 4 and also permits lightto reflect from the cornea 4 back out of the contact device 2 throughthe transparent on peripheral portion 36. Although the transparentperipheral portion 36 may consist entirely of an air gap, for reasons ofaccuracy and to provide smoother sliding of the movable central piece 16through the rigid annular member 12, it is preferred that a transparentsolid material constitute the transparent peripheral portion 36.Exemplary transparent solid materials include polymethyl methacrylate,glass, hard acrylic, plastic polymers, and the like.

The magnetically responsive element 26 preferably comprises an annularmagnet having a central sight hole 38 through which a patient is able tosee while the contact device 2 is located on the patient's cornea 4. Thecentral sight hole 38 is aligned with the transparent area 22 of theflexible membrane 14 and is preferably at least 1-2 millimeters indiameter.

Although the preferred embodiment includes an annular magnet as themagnetically responsive element 26, it is understood that various othermagnetically responsive elements 26 may be used, including variousferromagnetic materials and/or suspensions of magnetically responsiveparticles in liquid. The magnetically responsive element 26 may alsoconsist of a plurality of small bar magnets arranged in a circle, tothereby define an opening equivalent to the illustrated central sighthole 38. A transparent magnet may also be used.

A display 40 is preferably provided for numerically displaying theintraocular pressure detected by the system. The display 40 preferablycomprises a liquid crystal display (LCD) or light emitting diode (LED)display connected and responsive to the conversion unit 34 of thecalculation unit 10.

Alternatively, the display 40 can be arranged so as to give indicationsof whether the intraocular pressure is within certain ranges. In thisregard, the display 40 may include a green LED 40A, a yellow LED 40B,and a red LED 40C. When the pressure is within a predetermined highrange, the red LED 40C is illuminated to indicate that medical attentionis needed. When the intraocular pressure is within a normal range, thegreen LED 40A is illuminated. The yellow LED 40B is illuminated when thepressure is between the normal range and the high range to indicate thatthe pressure is somewhat elevated and that, although medical attentionis not currently needed, careful and frequent monitoring is recommended.

Preferably, since different patients may have different sensitivities orreactions to the same intraocular pressure, the ranges corresponding toeach LED 40A,40B,40C are calibrated for each patient by an attendingphysician. This way, patients who are more susceptible to consequencesfrom increased intraocular pressure may be alerted to seek medicalattention at a pressure less than the pressure at which otherless-susceptible patients are alerted to take the same action. The rangecalibrations may be made using any known calibration device 40Dincluding variable gain amplifiers or voltage divider networks withvariable resistances.

The detecting arrangement 8 preferably comprises an optical detectionsystem including two primary beam emitters 44,46; two light sensors48,50; and two converging lenses 52,54. Any of a plurality ofcommercially available beam emitters may be used as emitters 44,46,including low-power laser beam emitting devices and infra-red (IR) beamemitting devices. Preferably, the device 2 and the primary beam emitters44,46 are arranged with respect to one another so that each of theprimary beam emitters 44,46 emits a primary beam of light toward thecornea through the transparent area 22 of the device and so that theprimary beam of light is reflected back through the device 2 by thecornea 4 to thereby produce reflected beams 60,62 of light with adirection of propagation dependent upon the amount of applanation of thecornea. The two light sensors 48,50 and two converging lenses 52,54 arepreferably arranged so as to be aligned with the reflected beams 60,62of light only when the predetermined amount of applanation of the cornea4 has been achieved. Preferably, the primary beams 56,58 pass throughthe substantially transparent peripheral portion 36.

Although FIG. 1 shows the reflected beams 60,62 of light diverging awayfrom one another and well away from the two converging lenses 52,54 andlight sensors 48,50, it is understood that as the cornea 4 becomesapplanated the reflected beams 60,62 will approach the two light sensors48,50 and the two converging lenses 52,54. When the predetermined amountof applanation is achieved, the reflected beams 60,62 will be directlyaligned with the converging lenses 52,54 and the sensors 48,50. Thesensors 48,50 are therefore able to detect when the predetermined amountof applanation is achieved by merely detecting the presence of thereflected beams 60,62. Preferably, the predetermined amount ofapplanation is deemed to exist when all of the sensors 48,50 receive arespective one of the reflected beams 60,62.

Although the illustrated arrangement is generally effective using twoprimary beam emitters 44,46 and two light sensors 48,50, better accuracycan be achieved in patients with astigmatisms by providing four beamemitters and four light sensors arranged orthogonally with respect toone another about the longitudinal axis of the actuation apparatus 6. Asin the case with two beam emitters 44,46 and light sensors 48,50, thepredetermined amount of applanation is preferably deemed to exist whenall of the sensors receive a respective one of the reflected beams.

A sighting arrangement is preferably provided for indicating when theactuation apparatus 6 and the detecting arrangement 8 are properlyaligned with the device 2. Preferably, the sighting arrangement includesthe central sight hole 38 in the movable central piece 16 through whicha patient is able to see while the device 2 is located on the patient'scornea 4. The central sight hole 38 is aligned with the transparent area22. In addition, the actuation apparatus 6 includes a tubular housing 64having a first end 66 for placement over an eye equipped with the device2 and a second opposite end 68 having at least one mark 70 arranged suchthat, when the patient looks through the central sight hole 38 at themark 70, the device 2 is properly aligned with the actuation apparatus 6and detecting arrangement 8.

Preferably, the second end 68 includes an internal mirror surface 72 andthe mark 70 generally comprises a set of cross-hairs. FIG. 3 illustratesthe view seen by a patient through the central sight hole 38 when thedevice 2 is properly aligned with the actuation apparatus 6 anddetecting arrangement 8. When proper alignment is achieved, thereflected image 74 of the central sight hole 38 appears in the mirrorsurface 72 at the intersection of the two cross-hairs which constitutethe mark 70. (The size of the image 74 is exaggerated in FIG. 3 to moreclearly distinguish it from other elements in the drawing).

Preferably, at least one light 75 is provided inside the tubular housing64 to illuminate the inside of the housing 64 and facilitate visualationof the cross-hairs and the reflected image 74. Preferably, the internalmirror surface 72 acts as a mirror only when the light 75 is on, andbecomes mostly transparent upon deactivation of the light 75 due todarkness inside the tubular housing 64. To that end, the second end 68of the tubular housing 68 may be manufactured using "one-way glass"which is often found in security and surveillance equipment.

Alternatively, if the device is to be used primarily by physicians,optometrists, or the like, the second end 68 may be merely transparent.If, on the other hand, the device is to be used by patients forself-monitoring, it is understood that the second end 68 may merelyinclude a mirror.

The system also preferably includes an optical distance measuringmechanism for indicating whether the device 2 is spaced at a properaxial distance from the actuation apparatus 6 and the detectingarrangement 8. The optical distance measurement mechanism is preferablyused in conjunction with the sighting arrangement.

Preferably, the optical distance measuring mechanism includes a distancemeasurement beam emitter 76 for emitting an optical distance measurementbeam 78 toward the device 2. The device 2 is capable of reflecting thedistance measurement beam 78 to produce a first reflected distancemeasurement beam 80. Arranged in the path of the first reflecteddistance measurement beam 80 is a preferably convex mirror 82. Theconvex mirror 82 reflects the first reflected distance measurement beam80 to create a second reflected distance measurement beam 84 and servesto amplify any variations in the first reflected beam's direction ofpropagation. The second reflected distance measurement beam 84 isdirected generally toward a distance measurement beam detector 86. Thedistance measurement beam detector 86 is arranged so that the secondreflected distance measurement beam 84 strikes a predetermined portionof the distance measurement beam detector 86 only when the device 2 islocated at the proper axial distance from the actuation apparatus 6 andthe detecting arrangement 8. When the proper axial distance is lacking,the second reflected distance measurement beam strikes another portionof the beam detector 86.

An indicator 88, such as an LCD or LED display, is preferably connectedand responsive to the beam detector 86 for indicating that the properaxial distance has been achieved only when the reflected distancemeasurement beam strikes the predetermined portion of the distancemeasurement beam detector.

Preferably, as illustrated in FIG. 1, the distance measurement beamdetector 86 includes a multi-filter optical element 90 arranged so as toreceive the second reflected distance measurement beam 84. Themulti-filter optical element 90 contains a plurality of optical filters92. Each of the optical filters 92 filters out a different percentage oflight, with the predetermined portion of the detector 86 being definedby a particular one of the optical filters 92 and a filtering percentageassociated therewith.

The distance measurement beam detector 86 further includes a beamintensity detection sensor 94 for detecting the intensity of the secondreflected distance measurement beam 84 after the beam 84 passes throughthe multi-filter optical element 90. Since the multi-filter opticalelement causes this intensity to vary with axial distance, the intensityis indicative of whether the device 2 is at the proper distance from theactuation apparatus 6 and the detecting arrangement 8.

A converging lens 96 is preferably located between the multi-filteroptical element 90 and the beam intensity detection sensor 94, forfocussing the second reflected distance measurement beam 84 on the beamintensity detection sensor 94 after the beam 84 passes through themulti-filter optical element 90.

Preferably, the indicator 88 is responsive to the beam intensitydetection sensor 94 so as to indicate what corrective action should betaken, when the device 2 is not at the proper axial distance from theactuation apparatus 6 and the detecting arrangement 8, in order toachieve the proper distance. The indication given by the indicator 88 isbased on the intensity and which of the plurality of optical filters 92achieves the particular intensity by virtue of a filtering percentageassociated therewith.

For example, when the device 2 is excessively far from the actuationapparatus 6, the second reflected distance measurement beam 84 passesthrough a dark one of the filters 92. There is consequently a reductionin beam intensity which causes the beam intensity detection sensor 94 todrive the indicator 88 with a signal indicative of the need to bring thedevice 2 closer to the actuation apparatus. The indicator 88 responds tothis signal by communicating the need to a user of the system.

Alternatively, the signal indicative of the need to bring the device 2closer to the actuation apparatus can be applied to a computer whichperforms corrections automatically.

In like manner, when the device 2 is excessively close to the actuationapparatus 6, the second reflected distance measurement beam 84 passesthrough a lighter one of the filters 92. There is consequently anincrease in beam intensity which causes the beam intensity detectionsensor 94 to drive the indicator 88 with a signal indicative of the needto move the device 2 farther from the actuation apparatus. The indicator88 responds to this signal by communicating the need to a user of thesystem.

In addition, computer-controlled movement of the actuation apparatusfarther away from the device 2 may be achieved automatically byproviding an appropriate computer-controlled moving mechanism responsiveto the signal indicative of the need to move the device 2 farther fromthe actuation apparatus.

With reference to FIG. 3, the indicator 88 preferably comprises threeLEDs arranged in a horizontal line across the second end 68 of thehousing 64. When illuminated, the left LED 88a, which is preferablyyellow, indicates that the contact device 2 is too far from theactuation apparatus 6 and the detecting arrangement 8. Similarly, whenilluminated, the right LED 88b, which is preferably red, indicates thatthe contact device 2 is too close to the actuation apparatus 6 and thedetecting arrangement 8. When the proper distance is achieved, thecentral LED 88c is illuminated. Preferably, the central LED 88c isgreen. The LEDs 88a-88c are selectively illuminated by the beamintensity detection sensor 94 in response to the beam's intensity.

Although FIG. 1 illustrates an arrangement of filters 92 wherein areduction in intensity signifies a need to move the device closer, it isunderstood that the present invention is not limited to such anarrangement. The multi-filter optical element 90, for example, may bereversed so that the darkest of the filters 92 is positioned adjacentthe end 68 of the tubular housing 64. When such an arrangement is used,an increase in beam intensity would signify a need to move the device 2farther away from the actuation apparatus 6.

Preferably, the actuation apparatus 6 (or at least the coil 30 thereof)is slidably mounted within the housing 64 and a knob and gearing (e.g.,rack and pinion) mechanism are provided for selectively moving theactuation apparatus 6 (or coil 30 thereof) axially through the housing64 in a perfectly linear manner until the appropriate axial distancefrom the contact device 2 is achieved. When such an arrangement isprovided, the first end 66 of the housing 64 serves as a positioningmechanism for the contact device 2 against which the patient presses thefacial area surrounding eye to be examined. once the facial area restsagainst the first end 66, the knob and gearing mechanism are manipulatedto place the actuation apparatus 6 (or coil 30 thereof) at the properaxial distance from the contact device 2.

Although facial contact with the first end 66 enhances stability, it isunderstood that facial contact is not an essential step in utilizing thepresent invention.

The system also preferably includes an optical alignment mechanism forindicating whether the device 2 is properly aligned with the actuationapparatus 6 and the detecting arrangement 8. The optical alignmentmechanism includes two alignment beam detectors 48',50' for respectivelydetecting the reflected beams 60,62 of light prior to any applanation.The alignment beam detectors 48',50' are arranged so that the reflectedbeams 60,62 of light respectively strike a predetermined portion of thealignment beam detectors 48',50' prior to applanation only when thedevice 2 is properly aligned with respect to the actuation apparatus 6and the detecting arrangement 8. When the device 2 is not properlyaligned, the reflected beams 60,62 strike another portion of thealignment beam detectors 48',50', as will be described hereinafter.

The optical alignment mechanism further includes an indicatorarrangement responsive to the alignment beam detectors 48',50'. Theindicator arrangement preferably includes a set of LEDs 98,100,102,104which indicate that the proper alignment has been achieved only when thereflected beams 60,62 of light respectively strike the predeterminedportion of the alignment beam detectors 48',50' prior to applanation.

Preferably, each of the alignment beam detectors 48',50' includes arespective multi-filter optical element 106,108. The multi-filteroptical elements 106,108 are arranged so as to receive the reflectedbeams 60,62 of light. Each multi-filter optical element 106,108 containsa plurality of optical filters 110₁₀ -110₉₀ (FIGS. 4 and 5), each ofwhich filters out a different percentage of light. In FIGS. 4 and 5, thedifferent percentages are labeled between 10 and 90 percent inincrements of ten percent. It is understood, however, that many otherarrangements and increments will suffice.

For the illustrated arrangement, it is preferred that the centrallylocated filters 110₅₀ which filter out 50% of the light represent thepredetermined portion of each alignment beam detector 48',50'. Properalignment is therefore deemed to exist when the reflected beams 60,62 oflight pass through the filters 110₅₀ and the intensity of the beams60,62 is reduced by 50%.

Each of the alignment beam detectors 48',50' also preferably includes abeam intensity detector 112,114 for respectively detecting the intensityof the reflected beams 60,62 of light after the reflected beams 60,62 oflight pass through the multi-filter optical elements 106,108. Theintensity of each beam is indicative of whether the device 2 is properlyaligned with respect to the actuation apparatus 6 and the detectingarrangement.

A converging lens 116,118 is preferably located between eachmulti-filter optical element 106,108 and its respective beam intensitydetector 112,114. The converging lens 116,118 focusses the reflectedbeams 60,62 of light onto the beam intensity detectors 112,114 after thereflected beams 60,62 pass through the multi-filter optical elements106,108.

Each of the beam intensity detectors 112,114 has its output connected toan alignment beam detection circuit which, based on the respectiveoutputs from the beam intensity detectors 112,114, determines whetherthere is proper alignment, and if not, drives the appropriate one orones of the LEDs 98,100,102,104 to indicate the corrective action whichshould be taken.

As illustrated in FIG. 3, the LEDs 98,100,102,104 are respectivelyarranged above, to the right of, below, and to the left of theintersection of the cross-hairs 70. No LEDs 98,100,102,104 areilluminated unless there is a misalignment. Therefore, a lack ofillumination indicates that the device 2 is properly aligned with theactuation apparatus 6 and the detecting arrangement 8.

When the device 2 on the cornea 4 is too high, the beams 56,58 of lightstrike a lower portion of the cornea 4 and because of the cornea'scurvature, are reflected in a more downwardly direction. The reflectedbeams 60,62 therefore impinge on the lower half of the multi-filterelements 106,108, and the intensity of each reflected beam 60,62 isreduced by no more than 30%. The respective intensity reductions arethen communicated to the alignment detection circuit 120 by the beamintensity detectors 112,114. The alignment detection circuit 120interprets this reduction of intensity to result from a misalignmentwherein the device 2 is too high. The alignment detection circuit 120therefore causes the upper LED 98 to illuminate. Such illuminationindicates to the user that the device 2 is too high and must be loweredwith respect to the actuation apparatus 6 and the detecting arrangement8.

Similarly, when the device 2 on the cornea 4 is too low, the beams 56,58of light strike an upper portion of the cornea 4 and because of thecornea's curvature, are reflected in a more upwardly direction. Thereflected beams 60,62 therefore impinge on the upper half of themulti-filter elements 106,108, and the intensity of each reflected beam60,62 is reduced by at least 70%. The respective intensity reductionsare then communicated to the alignment detection circuit 120 by the beamintensity detectors 112,114. The alignment detection circuit 120interprets this particular reduction of intensity to result from amisalignment wherein the device 2 is too low. The alignment detectioncircuit 120 therefore causes the lower LED 102 to illuminate. Suchillumination indicates to the user that the device 2 is too low and mustbe raised with respect to the actuation apparatus 6 and the detectingarrangement 8.

With reference to FIG. 1, when the device 2 is too far to the right, thebeams 56,58 strike a more leftward side of the cornea 4 and because ofthe cornea's curvature, are reflected in a more leftward direction. Thereflected beams 60,62 therefore impinge on the left halves of themulti-filter elements 106,108. Since the filtering percentages decreasefrom left to right in multi-filter element 106 and increase from left toright in multifilter element 108, there will be a difference in theintensities detected by the beam intensity detectors 112,114. Inparticular, the beam intensity detector 112 will detect less intensitythan the beam intensity detector 114. The different intensities are thencommunicated to the alignment detection circuit 120 by the beamintensity detectors 112,114. The alignment detection circuit 120interprets the intensity difference wherein the intensity at the beamintensity detector 114 is higher than that at the beam intensitydetector 112, to result from a misalignment wherein the device 2 is toofar to the right in FIG. 1 (too far to the left in FIG. 3). Thealignment detection circuit 120 therefore causes the left LED 104 toilluminate. Such illumination indicates to the user that the device 2 istoo far to the left (in FIG. 3) and must be moved to the right (left inFIG. 1) with respect to the actuation apparatus 6 and the detectingarrangement 8.

Similarly, when the device 2 in FIG. 1 is too far to the left, the beams56,58 strike a more rightward side of the cornea 4 and because of thecornea's curvature, are reflected in a more rightwardly direction. Thereflected beams 60,62 therefore impinge on the right halves of themulti-filter elements 106,108. Since the filtering percentages decreasefrom left to right in multi-filter element 106 and increase from left toright in multifilter element 108, there will be a difference in theintensities detected by the beam intensity detectors 112,114. Inparticular, the beam intensity detector 112 will detect more intensitythan the beam intensity detector 114. The different intensities are thencommunicated to the alignment detection circuit 120 by the beamintensity detectors 112,114. The alignment detection circuit 120interprets the intensity difference wherein the intensity at the beamintensity detector 114 is lower than that at the beam intensity detector112, to result from a misalignment wherein the device 2 is too far tothe left in FIG. 1 (too far to the right in FIG. 3). The alignmentdetection circuit 120 therefore causes the right LED 100 to illuminate.Such illumination indicates to the user that the device 2 is too far tothe right (in FIG. 3) and must be moved to the left (right in FIG. 1)with respect to the actuation apparatus 6 and the detecting arrangement8.

The combination of LEDs 98,100,102,104 and the alignment detectioncircuit 120 therefore constitutes a display arrangement which isresponsive to the beam intensity detectors 112,114 and which indicateswhat corrective action should be taken, when the device 2 is notproperly aligned, in order to achieve proper alignment. Preferably, thesubstantially transparent peripheral portion 36 of the movable centralpiece 16 is wide enough to permit passage of the beams 56,58 to thecornea 4 even during misalignment.

It is understood that automatic alignment correction may be provided viacomputer-controlled movement of the actuation apparatus upwardly,downwardly, to the right, and/or to the left, which computer-controlledmovement may be generated by an appropriate computer-controlled movingmechanism responsive to the optical alignment mechanism.

The optical alignment mechanism is preferably used in conjunction withthe sighting arrangement, so that the optical alignment mechanism merelyprovides indications of minor alignment corrections while the sightingarrangement provides an indication of major alignment corrections. It isunderstood, however, that the optical alignment mechanism can be used inlieu of the sighting mechanism if the substantially transparentperipheral portion 36 is made wide enough.

Although the foregoing alignment mechanism uses the same reflected beams60,62 used by the detecting arrangement 8, it is understood thatseparate alignment beam emitters may be used in order to provideseparate and distinct alignment beams. The foregoing arrangement ispreferred because it saves the need to provide additional emitters andthus is less expensive to manufacture.

Nevertheless, optional alignment beam emitters 122,124 are illustratedin FIG. 1. The alignment mechanism using these optional alignment beamemitters 122,124 would operate in essentially the same manner as itscounterpart which uses the reflected beams 60,62.

In particular, each of the alignment beam emitters 122,124 emits anoptical alignment beam toward the device 2. The alignment beam isreflected by the cornea 4 to produce a reflected alignment beam. Thealignment beam detectors 48',50' are arranged so as to receive, not thereflected beams 60,62 of light, but rather the reflected alignment beamswhen the alignment beam emitters 122,124 are present. More specifically,the reflected alignment beams strike a predetermined portion of eachalignment beam detector 48',50' prior to applanation only when thedevice 2 is properly aligned with respect to the actuation apparatus 6and the detecting arrangement 8. The rest of the system preferablyincludes the same components and operates in the same manner as thesystem which does not use the optional. alignment beam emitters 122,124.

The system may further include an applicator for gently placing thecontact device 2 on the cornea 4. As illustrated in FIGS. 5A-5F, apreferred embodiment of the applicator 127 includes an annular piece127A at the tip of the applicator 127. The annular piece 127A matchesthe shape of the movable central piece 16. Preferably, the applicator127 also includes a conduit 127CN having an open end which opens towardthe annular piece 127A. An opposite end of the conduit 127CN isconnected to a squeeze bulb 127SB. The squeeze bulb 127SB includes aone-way valve 127V which permits the flow of air into the squeeze bulb127SB, but prevents the flow of air out of the squeeze bulb 127SBthrough the valve 127V. When the squeeze bulb 127SB is squeezed and thenreleased, a suction effect is created at the open end of the conduit127CN as the squeeze bulb 127SB tries to expand to its pre-squeezeshape. This suction effect may be used to retain the contact device 2 atthe tip of the applicator 127.

In addition, a pivoted lever system 127B is arranged to detach themovable central piece 16 from the annular piece 127A when a knob 127C atthe base of the applicator 127 is pressed, thereby nudging the contactdevice 2 away from the annular piece 127A.

Alternatively, the tip of the applicator 127 may be selectivelymagnetized and demagnetized using electric current flowing through theannular piece 127A. This arrangement replaces the pivoted lever system127B with a magnetization mechanism capable of providing a magneticfield which repels the movable central piece 16, thereby applying thecontact device 2 to the cornea 4.

A preferred circuit arrangement for implementing the above combinationof elements is illustrated schematically in FIG. 6. According to thepreferred circuit arrangement, the beam intensity detectors 112,114comprise a pair of photosensors which provide a voltage outputproportional to the detected beam intensity. The output from each beamintensity detector 112,114 is respectively connected to thenon-inverting input terminal of a filtering amplifier 126,128. Theinverting terminals of the filtering amplifiers 126,128 are connected toground. The amplifiers 126,128 therefore provide a filtering andamplification effect.

In order to determine whether proper vertical alignment exists, theoutput from the filtering amplifier 128 is applied to an inverting inputterminal of a vertical alignment comparator 130. The vertical alignmentcomparator 130 has its non-inverting input terminal connected to areference voltage Vref₁. The reference voltage Vref₁ is selected so thatit approximates the output from the filtering amplifier 128 whenever thelight beam 62 strikes the central row of filters 110₄₀₋₆₀ of themulti-filter optical element 108 (i.e., when the proper verticalalignment is achieved).

Consequently, the output from the comparator 130 is approximately zerowhen proper vertical alignment is achieved, is significantly negativewhen the contact device 2 is too high, and is significantly positivewhen the contact device 2 is too low. This output from the comparator130 is then applied to a vertical alignment switch 132. The verticalalignment switch 132 is logically arranged to provide a positive voltageto an AND-gate 134 only when the output from the comparator 130 isapproximately zero, to provide a positive voltage to the LED 98 onlywhen the output from the comparator 130 is negative, and to provide apositive voltage to the LED 102 only when the output from the comparator130 is positive. The LEDs 98,102 are thereby illuminated only when thereis a vertical misalignment and each illumination clearly indicates whatcorrective action should to be taken.

In order to determine whether proper horizontal alignment exists, theoutput from the filtering amplifier 126 is applied to a non-invertinginput terminal of a horizontal alignment comparator 136, while theinverting input terminal of the horizontal alignment comparator 136 isconnected to the output from the filtering amplifier 128. The comparator136 therefore produces an output which is proportional to the differencebetween the intensities detected by the beam intensity detectors112,114. This difference is zero whenever the light beams 60,62 strikethe central column of filters 110₂₀, 110₅₀, 110₈₀ of the multi-filteroptical elements 106,108 (i.e., when the proper horizontal alignment isachieved).

The output from the comparator 136 is therefore zero when the properhorizontal alignment is achieved, is negative when the contact device 2is too far to the right (in FIG. 1), and is positive when the contactdevice 2 is too far to the left (in FIG. 1). This output from thecomparator 130 is then applied to a horizontal alignment switch 138. Thehorizontal alignment switch 138 is logically arranged to provide apositive voltage to the AND-gate 134 only when the output from thecomparator 136 is zero, to provide a positive voltage to the LED 104only when the output from the comparator 136 is negative, and to providea positive voltage to the LED 100 only when the output from thecomparator 136 is positive. The LEDs 100, 104 are thereby illuminatedonly when there is a horizontal misalignment and each illuminationclearly indicates what corrective action should be taken.

In accordance with the preferred circuit arrangement illustrated in FIG.6, the beam intensity detection sensor 94 of the distance measurementbeam detector 86 includes a photosensor 140 which produces a voltageoutput proportional to the detected beam intensity. This voltage outputis applied to the non-inverting input terminal of a filtering amplifier142. The inverting terminal of the filtering amplifier 142 is connectedto ground. Accordingly, the filtering amplifier 142 filters andamplifies the voltage output from the photosensor 140. The output fromthe filtering amplifier 142 is applied to the non-inverting inputterminal of a distance measurement comparator 144. The comparator 144has its inverting terminal connected to a reference voltage Vref₂.Preferably, the reference voltage Vref₂ is selected so as to equal theoutput of the filtering amplifier 142 only when the proper axialdistance separates the contact device 2 from the actuation apparatus 6and detecting arrangement 8.

Consequently, the output from the comparator 144 is zero whenever theproper axial distance is achieved, is negative whenever the secondreflected beam 84 passes through a dark portion of the multi-filteroptical element 90 (i.e., whenever the axial distance is too great), andis positive whenever the second reflected beam 84 passes through a lightportion of the multi-filter optical element 90 (i.e., whenever the axialdistance is too short).

The output from the comparator 144 is then applied to a distancemeasurement switch 146. The distance measurement switch 146 drives theLED 88c with positive voltage whenever the output from the comparator144 is zero, drives the LED 88b only when the output from the comparator144 is positive, and drives the LED 88a only when the output from thecomparator 144 is negative. The LEDs 88a,88b are thereby illuminatedonly when the axial distance separating the contact device 2 from theactuation apparatus 6 and the detecting arrangement 8 is improper. Eachillumination clearly indicates what corrective action should be taken.Of course, when the LED 88c is illuminated, no corrective action isnecessary.

With regard to the detecting arrangement 8, the preferred circuitarrangement illustrated in FIG. 6 includes the two light sensors 48,50.The outputs from the light sensors 48,50 are applied to and added by anadder 147. The output from the adder 147 is then applied to thenon-inverting input terminal of a filtering amplifier 148. The invertinginput terminal of the same amplifier 148 is connected to ground. As aresult, the filtering amplifier 148 filters and amplifies the sum of theoutput voltages from the light sensor 48,50. The output from thefiltering amplifier 148 is then applied to the non-inverting inputterminal of an applanation comparator 150. The inverting input terminalof the applanation comparator 150 is connected to a reference voltageVref₃. Preferably, the reference voltage Vref₃ is selected so as toequal the output from the filtering amplifier 148 only when thepredetermined amount of applanation is achieved (i.e., when thereflected beams 60,62 strike the light sensors 48,50). The output fromthe applanation comparator 150 therefore remains negative until thepredetermined amount of applanation is achieved.

The output from the applanation comparator 150 is connected to anapplanation switch 152. The applanation switch 152 provides a positiveoutput voltage when the output from the applanation comparator 150 isnegative and terminates its positive output voltage whenever the outputfrom the applanation comparator 150 becomes positive.

Preferably, the output from the applanation switch 152 is connected toan applanation speaker 154 which audibly indicates when thepredetermined amount of applanation has been achieved. In particular,the speaker 154 is activated whenever the positive output voltage fromthe applanation, switch 152 initially disappears.

In the preferred circuit of FIG. 6, the coil 30 is electricallyconnected to the current producing circuitry 32 which, in turn, includesa signal generator capable of producing the progressively increasingcurrent in the coil 30. The current producing circuitry 32 is controlledby a start/stop switch 156 which is selectively activated anddeactivated by an AND-gate 158.

The AND-gate 158 has two inputs, both of which must exhibit positivevoltages in order to activate the start/stop switch 156 and currentproducing circuitry 32. A first input 160 of the two inputs is theoutput from the applanation switch 152. Since the applanation switch 152normally has a positive output voltage, the first input 160 remainspositive and the AND-gate is enabled at least with respect to the firstinput 160. However, whenever the predetermined amount of applanation isachieved (i.e. whenever the positive output voltage is no longer presentat the output from the applanation switch 152), the AND-gate 158deactivates the current producing circuitry 32 via the start/stop switch156.

The second input to the AND-gate 158 is the output from another AND-gate162. The other AND-gate 162 provides a positive output voltage only whena push-action switch 164 is pressed and only when the contact device 2is located at the proper axial distance from, and is properly alignedboth vertically and horizontally with, the actuation apparatus 6 and thedetecting arrangement 8. The current producing circuitry 32 thereforecannot be activated unless there is proper alignment and the properaxial distance has been achieved. In order to achieve such operation,the output from the AND-gate 134 is connected to a first input of theAND-gate 162 and the push-action switch 164 is connected to the secondinput of the AND-gate 162.

A delay element 163 is located electrically between the AND-gate 134 andthe AND-gate 162. The delay element 163 maintains a positive voltage atthe first input terminal to the AND-gate 162 for a predetermined periodof time after a positive voltage first appears at the output terminal ofthe AND-gate 134. The primary purpose of the delay element 163 is toprevent deactivation of the current producing circuitry 32 which wouldotherwise occur in response to changes in the propagation direction ofthe reflected beams 60,62 during the initial stages of applanation. Thepredetermined period of time is preferably selected pursuant to themaximum amount of time that it could take to achieve the predeterminedamount of applanation.

According to the preferred circuitry illustrated in FIG. 6, misalignmentand improper axial separation of the contact device 2 with respect tothe actuation apparatus 6 and detecting arrangement 8 is audiblyannounced by a speaker 166 and causes deactivation of a display 167. Thedisplay 167 and speaker 166 are connected and responsive to an AND-gate168. The AND-gate 168 has an inverting input connected to thepush-action switch 164 and another input connected to a three-inputOR-gate 170.

Therefore, when the push-action switch 164 is activated, the invertinginput terminal of the AND-gate 168 prevents a positive voltage fromappearing at the output from the AND-gate 168. Activation of the speaker166 is thereby precluded. However, when the push-action switch is notactivated, any positive voltage at any of the three inputs to theOR-gate 170 will activate the speaker 166. The three inputs to theOR-gate 170 are respectively connected to outputs from three otherOR-gates 172,174,176. The OR-gates 172,174,176, in turn, have theirinputs respectively connected to the LEDs 100,104, LEDs 98,102, and LEDs88a,88b. Therefore, whenever any one of these LEDs 88a, 88b, 98, 100,102, 104 is activated, the OR-gate 170 produces a positive outputvoltage. The speaker 166, as a result, will be activated whenever anyone of the LEDs 88a,88b,98,100,102,104 is activated while thepush-action switch 164 remains deactivated.

Turning now to the current producing circuitry 32, the output from thecurrent producing circuitry 32 is connected to the coil 30. The coil 30,in turn, is connected to a current-to-voltage transducer 178. The outputvoltage from the current-to-voltage transducer 178 is proportional tothe current flowing through the coil 30 and is applied to thecalculation unit 10.

The calculation unit 10 receives the output voltage from the transducer178 and converts this output voltage indicative of current to an outputvoltage indicative of intraocular pressure. Initially, an output voltagefrom the filtering amplifier 142 indicative of the axial distanceseparating the contact device 2 from the actuation apparatus 6 and thedetecting arrangement 8, is multiplied by a reference voltage Vref₄using a multiplier 180. The reference voltage Vref₄ represents adistance calibration constant. The output from the multiplier 180 isthen squared by a multiplier 182 to create an output voltage indicativeof distance squared (d²).

The output from the multiplier 182 is then supplied to an input terminalof a divider 184. The other input terminal of the divider 184 receivesthe output voltage indicative of current from the current-to-voltagetransducer 178. The divider 184 therefore produces an output voltageindicative of the current in the coil 30 divided by the distance squared(I/d²).

The output voltage from the divider 184 is then applied to a multiplier186. The multiplier 186 multiplies the output voltage from the divider184 by a reference voltage Vref₅. The reference voltage Vref₅corresponds to a conversion factor for converting the value of (I/d²) toa value indicative of force in Newtons being applied by the movablecentral piece 16 against the cornea 4. The output voltage from themultiplier 186 is therefore indicative of the force in Newtons beingapplied by the movable central piece 16 against the cornea.

Next, the output voltage from the multiplier 186 is applied to an inputterminal of a divider 188. The other input terminal of the divider 188receives a reference voltage Vref₆. The reference voltage Vref₆corresponds to a calibration constant for converting force (in Newtons)to pressure (in Pascals) depending on the surface area of the movablecentral piece's substantially flat inner side 24. The output voltagefrom the divider 188 is therefore indicative of the pressure (inPascals) being exerted by the cornea 4 against the inner side of themovable central piece 16 in response to displacement of the movablecentral piece 16.

Since the pressure exerted by the cornea 4 depends upon the surface areaof the substantially flat inner side 24, the output voltage from thedivider 188 is indicative of intraocular pressure only when the cornea 4is being applanated by the entire surface area of the inner side 24.This, in turn, corresponds to the predetermined amount of applanation.

Preferably, the output voltage indicative of intraocular pressure isapplied to an input terminal of a multiplier 190. The multiplier 190 hasanother input terminal connected to a reference voltage Vref₇. Thereference voltage Vref₇ corresponds to a conversion factor forconverting pressure in Pascals to pressure in millimeters of mercury(mmHg). The voltage output from the multiplier 190 therefore isindicative of intraocular pressure in millimeters of mercury (mmHg)whenever the predetermined amount of applanation is achieved.

The output voltage from the multiplier 190 is then applied to thedisplay 167 which provides a visual display of intraocular pressurebased on this output voltage. Preferably, the display 167 or calculationunit 10 includes a memory device 33 which stores a pressure valueassociated with the output voltage from the multiplier 190 whenever thepredetermined amount of applanation is achieved. Since the currentproducing circuitry 32 is automatically and immediately deactivated uponachieving the predetermined amount of applanation, the intraocularpressure corresponds to the pressure value associated with the peakoutput voltage from the multiplier 190. The memory therefore can betriggered to store the highest pressure value upon detecting a drop inthe output voltage from the multiplier 190. Preferably, the memory isautomatically reset prior to any subsequent measurements of intraocularpressure.

Although FIG. 6 shows the display 167 in digital form, it is understoodthat the display 167 may have any known form. The display 167 may alsoinclude the three LEDs 40A,40B,40C illustrated in FIG. 1 which give avisual indication of pressure ranges which, in turn, are calibrated foreach patient.

As indicated above, the illustrated calculation unit 10 includesseparate and distinct multipliers 180,182,186,190 and dividers 184,188for converting the output voltage indicative of current into an outputvoltage indicative of intraocular pressure in millimeters of mercury(mmHg). The separate and distinct multipliers and dividers arepreferably provided so that variations in the system's characteristicscan be compensated for by appropriately changing the reference voltagesVref₄, Vref₅, Vref₆ and/or Vref₇. It is understood, however, that whenall of the system's characteristics remain the same (e.g., the surfacearea of the inner side 24 and the desired distance separating thecontact device 2 from the actuation apparatus 6 and detectingarrangement 8) and the conversion factors do not change, that a singleconversion factor derived from the combination of each of the otherconversion factors can be used along with a single multiplier or dividerto achieve the results provided by the various multipliers and dividersshown in FIG. 6.

Although the above combination of elements is generally effective ataccurately measuring intraocular pressure in a substantial majority ofpatients, some patients have unusually thin or unusually thick corneas.This, in turn, may cause slight deviations in the measured intraocularpressure. In order to compensate for such deviations, the circuitry ofFIG. 6 may also include a variable gain amplifier 191 (illustrated inFIG. 7A) connected to the output from the multiplier 190. For themajority of patients, the variable gain amplifier 191 is adjusted toprovide a gain (g) of one. The variable gain amplifier 191 thereforewould have essentially no effect on the output from the multiplier 190.

However, for patients with unusually thick corneas, the gain (g) isadjusted to a positive gain less than one. A gain (g) of less than oneis used because unusually thick corneas are more resistant toapplanation and consequently result in a pressure indication thatexceeds, albeit by a small amount, the actual intraocular pressure. Theadjustable gain amplifier 191 therefore reduces the output voltage fromthe multiplier 190 by a selected percentage proportional to the cornea'sdeviation from normal corneal thickness.

For patients with unusually thin corneas, the opposite effect would beobserved. Accordingly, for those patients, the gain (g) is adjusted to apositive gain greater than one so that the adjustable gain amplifier 191increases the output voltage from the multiplier 190 by a selectedpercentage proportional to the cornea's deviation from normal cornealthickness.

Preferably, the gain (g) is manually selected for each patient using anyknown means for controlling the gain of a variable gain amplifier, forexample, a potentiometer connected to a voltage source. As indicatedabove, the particular gain (g) used depends on the thickness of eachpatient's cornea which, in turn, can be determined using known cornealpachymetry techniques. Once the corneal thickness is determined, thedeviation from the normal thickness is calculated and the gain (g) isset accordingly.

Alternatively, as illustrated in FIG. 7B, the gain (g) may be selectedautomatically by connecting an output (indicative of corneal thickness)from a known pachymetry apparatus 193 to a buffer circuit 195. Thebuffer circuit 195 converts the detected corneal thickness to a gainsignal associated with the detected thickness'deviation from the normalcorneal thickness. In particular, the gain signal produces a gain (g) ofone when the deviation is zero, produces a gain (g) greater than onewhen the detected corneal thickness is less than the normal thickness,and produces a gain (g) less than one when the detected cornealthickness is greater than the normal thickness.

Although FIGS. 7A and 7B illustrate a configuration which compensatesonly for corneal thickness, it is understood that similar configurationscan be used to compensate for corneal curvature, eye size, ocularrigidity, and the like. For levels of corneal curvature which are higherthan normal, the gain would be less than one. The gain would be greaterthan one for levels of corneal curvature which are flatter than normal.Typically, each increase in one diopter of corneal curvature isassociated with a 0.34 mm Hg increase in pressure. The intraocularpressure rises 1 mm Hg for very 3 diopters. The gain therefore can beapplied in accordance with this general relationship.

In the case of eye size compensation, larger than normal eyes wouldrequire a gain which is less than one, while smaller than normal eyeswould require a gain which is greater than one.

For patients with "stiffer" than normal ocular rigidities, the gain isless than one, but for patients with softer ocular rigidities, the gainis greater than one.

As when compensating for corneal thickness, the gain may be manuallyselected for each patient, or alternatively, the gain may be selectedautomatically by connecting the apparatus of the present invention to aknown keratometer when compensating for corneal curvature, and/or aknown biometer when compensating for eye size.

Despite not being illustrated, it is understood that the system includesa power supply mechanism for selectively powering the system usingeither batteries or household AC current.

Operation of the preferred circuitry will now be described. Initially,the contact device 2 is mounted on the corneal surface of a patient andtends to locate itself centrally at the front of the cornea 4 inessentially the same way as conventional contact lenses. The patientthen looks through the central sight hole 38 at the intersection of thecross-hairs which define the mark 70, preferably, while the light 75provided inside the tubular housing 64 is illuminated to facilitatevisualization of the cross-hairs and the reflected image 74. A roughalignment is thereby achieved.

Next, the preferred circuitry provides indications of misalignment orimproper axial distance should either or both exist. The patientresponds to such indications by taking the indicated corrective action.

Once proper alignment is achieved and the proper axial distance existsbetween the actuation apparatus 6 and the contact device 2, push-actionswitch 164 is activated and the AND-gate 158 and start/stop switch 156activate the current producing circuitry 32. In response to activation,the current producing circuitry 32 generates the progressivelyincreasing current in the coil 30. The progressively increasing currentcreates a progressively increasing magnetic field in the coil 30. Theprogressively increasing magnetic field, in turn, causes axialdisplacement of the movable central piece 16 toward the cornea 4 byvirtue of the magnetic field's repulsive effect on the magneticallyresponsive element 26. Since axial displacement of the movable centralpiece 16 produces a progressively increasing applanation of the cornea4, the reflected beams 60,62 begin to swing angularly toward the lightsensors 48,50. Such axial displacement and increasing applanationcontinues until both reflected beams 60,62 reach the light sensors 48,50and the predetermined amount of applanation is thereby deemed to exist.At that instant, the current producing circuit 32 is deactivated by theinput 160 to AND-gate 158; the speaker 154 is momentarily activated togive an audible indication that applanation has been achieved; and theintraocular pressure is stored in the memory device 33 and is displayedon display 167.

Although the above-described and illustrated embodiment includes variouspreferred elements, it is understood that the present invention may beachieved using various other individual elements. For example, thedetecting arrangement 8 may utilize various other elements, includingelements which are typically utilized in the art of barcode reading.

With reference to FIGS. 8A and 8B, a contact device 2' may be providedwith a barcode-like pattern 300 which varies in response to displacementof the movable central piece 16'. FIG. 8A illustrates the preferredpattern 300 prior to displacement of the movable central piece 16'; andFIG. 8B shows the preferred pattern 300 when the predetermined amount ofapplanation is achieved. The detecting arrangement therefore wouldinclude a barcode reader directed generally toward the contact device 2'and capable of detecting the differences in the barcode pattern 300.

Alternatively, as illustrated in FIGS. 9A and 9E, the contact device 2'may be provided with a multi-color pattern 310 which varies in responseto displacement of the movable central piece 16'. FIG. 9A schematicallyillustrates the preferred color pattern 310 prior to displacement of themovable central piece 16', while FIG. 9B schematically shows thepreferred pattern 310 when the predetermined amount of applanation isachieved. The detecting arrangement therefore would include a beamemitter for emitting a beam of light toward the pattern 310 and adetector which receives a reflected beam from the pattern 310 anddetects the reflected color to determine whether applanation has beenachieved.

Yet another way to detect the displacement of the movable central piece16 is by using a two dimensional array photosensor that senses thelocation of a reflected beam of light. Capacitive and electrostaticsensors, as well as changes in magnetic field can then be used to encodethe position of the reflected beam and thus the displacement of themovable central piece 16.

According to yet another alternative embodiment illustrated in FIG. 10,a miniature LED 320 is inserted into the contact device 2'. Thepiezoelectric ceramic is driven by ultrasonic waves or is alternativelypowered by electromagnetic waves. The brightness of the miniature LED320 is determined by the current flowing through the miniature LED 320which, in turn, may be modulated by a variable resistance 330. Themotion of the movable central piece 16' varies the variable resistance330. Accordingly, the intensity of light from the miniature LED 320indicates the magnitude of the movable central piece's displacement. Aminiature, low-voltage primary battery 340 may be inserted into thecontact device 2' for powering the miniature LED 320.

With regard to yet another preferred embodiment of the presentinvention, it is understood that a tear film typically covers the eyeand that a surface tension resulting therefrom may cause underestimationof the intraocular pressure. Accordingly, the contact device of thepresent invention preferably has an inner surface of hydrophobicflexible material in order to decrease or eliminate this potentialsource of error.

It should be noted that the drawings are merely schematicrepresentations of the preferred embodiments. Therefore, the actualdimensions of the preferred embodiments and physical arrangement of thevarious elements is not limited to that which is illustrated. Variousarrangements and dimensions will become readily apparent to those ofordinary skill in the art. The size of the movable central piece, forexample, can be modified for use in animals or experimental techniques.Likewise, the contact device can be made with smaller dimensions for usewith infants and patients with eye lid abnormalities.

One preferred arrangement of the present invention includes a handleportion extending out from below the housing 64 and connected distallyto a platform. The platform acts as a base for placement on a planarsurface (e.g., a table), with the handle projecting up therefrom tosupport the actuation apparatus 6 above the planar surface.

INDENTATION

The contact device 2 and associated system illustrated in FIGS. 1-5 mayalso be used to detect intraocular pressure by indentation. Whenindentation techniques are used in measuring intraocular pressure, apredetermined force is applied against the cornea using an indentationdevice. Because of the force, the indentation device travels in towardthe cornea, indenting the cornea as it travels. The distance travelledby the indentation device into the cornea in response to thepredetermined force is known to be inversely proportional to intraocularpressure. Accordingly, there are various known tables which, for certainstandard sizes of indentation devices and standard forces, correlate thedistance travelled and intraocular pressure.

In utilizing the illustrated arrangement for indentation, the movablecentral piece 16 of the contact device 2 functions as the indentationdevice. In addition, the current producing circuit 32 is switched tooperate in an indentation mode. When switched to the indentation mode,the current producing circuit 32 supplies a predetermined amount ofcurrent through the coil 30. The predetermined amount of currentcorresponds to the amount of current needed to produce one of theaforementioned standard forces.

The predetermined amount of current creates a magnetic field in theactuation apparatus 6. This magnetic field, in turn, causes the movablecentral piece 16 to push inwardly against the cornea 4 via the flexiblemembrane 14. Once the predetermined amount of current has been appliedand a standard force presses against the cornea, it is necessary todetermine how far the movable central piece 16 moved into the cornea 4.

Accordingly, when measurement of intraocular pressure by indentation isdesired, the system illustrated in FIG. 1 further includes a distancedetection arrangement for detecting a distance travelled by the movablecentral piece 16, and a computation portion 199 in the calculation unit10 for determining intraocular pressure based on the distance travelledby the movable central piece 16 in applying the predetermined amount offorce.

A preferred indentation distance detection arrangement 200 isillustrated in FIGS. 11A and 11B and preferably includes a beam emitter202 and a beam sensor 204. Preferably, lenses 205 are disposed in theoptical path between the beam emitter 202 and beam sensor 204. The beamemitter 202 is arranged so as to emit a beam 206 of light toward themovable central piece 16. The beam 206 of light is reflected back fromthe movable central piece 16 to create a reflected beam 208. The beamsensor 204 is positioned so as to receive the reflected beam 208whenever the device 2 is located at the proper axial distance and inproper alignment with the actuation apparatus 6. Preferably, the properdistance and alignment are achieved using all or any combination of theaforementioned sighting mechanism, optical alignment mechanism andoptical distance measuring mechanism.

Once proper alignment and the proper axial distance are achieved, thebeam 206 strikes a first portion of the movable central piece 16, asillustrated in FIG. 11A. Upon reflection of the beam 206, the reflectedbeam 208 strikes a first portion of the beam sensor 204. In FIG. 11A,the first portion is located on the beam sensor 204 toward the rightside of the drawing.

However, as indentation progresses, the movable central piece 16 becomesmore distant from the beam emitter 202. This increase in distance isillustrated in FIG. 11A. Since the movable central piece 16 moveslinearly away, the beam 206 strikes progressively more to the left onthe movable central piece 16. The reflected beam 206 therefore shiftstoward the left and strikes 204 at a second portion which is to the leftof the first portion.

The beam sensor 204 is arranged so as to detect the shift in thereflected beam 206, which shift is proportional to the displacement ofthe movable central piece 16. Preferably, the beam sensor 204 includesan intensity responsive beam detector 212 which produces an outputvoltage proportional to the detected intensity of the reflected beam 208and an optical filter element 210 which progressively filters more lightas the light's point of incidence moves from one portion of the filterto an opposite portion.

In FIGS. 11A and 11B, the optical filter element 210 comprises a filterwith a progressively increasing thickness so that light passing througha thicker portion has a more significantly reduced intensity than lightpassing through a thinner portion of the filter. Alternatively, thefilter can have a constant thickness and progressively increasingfiltering density whereby a progressively increasing filtering effect isachieved as the point of incidence moves across a longitudinal length ofthe filter.

When, as illustrated in FIG. 11A, the reflected beam 208 passes througha thinnest portion of the optical filter element 210 (e.g., prior toindentation), the reflected beam's intensity is reduced by only a smallamount. The intensity responsive beam detector 212 therefore provides arelatively high output voltage indicating that no movement of themovable central piece 16 toward the cornea 4 has occurred.

However, as indentation progresses, the reflected beam 208 progressivelyshifts toward thicker portions of the optical filter element 210 whichfilter more light. The intensity of the reflected beam 208 thereforedecreases proportionally to the displacement of the movable centralpiece 16 toward the cornea 4. Since the intensity responsive beamdetector 212 produces an output voltage proportional to the reflectedbeam's intensity, this output voltage decreases progressively as thedisplacement of the movable central piece 16 increases. The outputvoltage from the intensity responsive beam detector 212 is thereforeindicative of the movable central piece's displacement.

Preferably, the computation portion 199 is responsive to the currentproducing circuitry 32 so that, once the predetermined amount of forceis applied, the output voltage from the beam detectors 212 is receivedby the computation portion 199. The computation portion then, based onthe displacement associated with the particular output voltage,determines intraocular pressure. Preferably, the memory 33 includes amemory location for storing a value indicative of the intraocularpressure.

Also, the computation portion 199 preferably has access to anelectronically or magnetically stored one of the aforementioned knowntables. Since the tables indicate which intraocular pressure correspondswith certain distances traveled by the movable central piece 16, thecomputation portion 199 is able to determine intraocular pressure bymerely determining which pressure corresponds with the distance traveledby the movable central piece 16.

The system of the present invention may also be used to calculate therigidity of the sclera. In particular, the system is first used todetermine intraocular pressure by applanation and then is used todetermine intraocular pressure by indentation. The differences betweenthe intraocular pressures detected by the two methods would then beindicative of the sclera's rigidity.

Although the foregoing description of the preferred systems generallyrefers to a combined system capable of detecting intraocular pressure byboth applanation and indentation, it is understood that a combinedsystem need not be created. That is, the system capable of determiningintraocular pressure by applanation may be constructed independentlyfrom a separate system for determining intraocular pressure byindentation and vice versa.

MEASURING HYDRODYNAMICS OF THE EYE

The indentation device of the present invention may also be utilized tonon-invasively measure hydrodynamics of an eye including outflowfacility. The method of the present invention preferably comprisesseveral steps including the following:

According to a first step, an indentation device is placed in contactwith the cornea. Preferably, the indentation device comprises thecontact device 2 illustrated in FIGS. 1 and 2A-2D.

Next, at least one movable portion of the indentation device is moved intoward the cornea using a first predetermined amount of force to achieveindentation of the cornea. When the indentation device is the contactdevice 2, the movable portion consists of the movable central piece 16.

An intraocular pressure is then determined based on a first distancetraveled toward the cornea by the movable portion of the indentationdevice during application of the first predetermined amount of force.Preferably, the intraocular pressure is determined using theaforementioned system for determining intraocular pressure byindentation.

Next, the movable portion of the indentation device is rapidlyreciprocated in toward the cornea and away from the cornea at a firstpredetermined frequency and using a second is predetermined amount offorce during movement toward the cornea to thereby force intraocularfluid out from the eye. The second predetermined amount of force ispreferably equal to or greater than the first predetermined amount offorce. It is understood, however, that the second predetermined amountof force may be less than the first predetermined amount of force. Thereciprocation, which preferably continues for 5 seconds, shouldgenerally not exceed 10 seconds induration.

The movable portion is then moved in toward the cornea using a thirdpredetermined amount of force to again achieve indentation of thecornea.

A second intraocular pressure is then determined based on a seconddistance traveled toward the cornea by the movable portion of theindentation device during application of the third predetermined amountof force. This second intraocular pressure is also preferably determinedusing the aforementioned system for determining intraocular pressure byindentation. Since intraocular pressure decreases as a result of forcingintraocular fluid out of the eye during the rapid reciprocation of themovable portion, it is generally understood that, unless the eye is sodefective that no fluid flows out therefrom, the second intraocularpressure will be less than the first intraocular pressure. Thisreduction in intraocular pressure is indicative of outflow facility.

Next, the movable portion of the indentation device is again rapidlyreciprocated in toward the cornea and away from the cornea, but at asecond predetermined frequency and using a fourth predetermined amountof force during movement toward the cornea. The fourth predeterminedamount of force is preferably equal or greater than the secondpredetermined amount of force. It is understood, however, that thefourth predetermined amount of force may be less than the secondpredetermined amount of force. Additional intraocular fluid is therebyforced out from the eye. This reciprocation, which also preferablycontinues for 5 seconds, should generally not exceed 10 seconds induration.

The movable portion is subsequently moved in toward the cornea using afifth predetermined amount of force to again achieve indentation of thecornea.

Thereafter, a third intraocular pressure is determined based on a thirddistance traveled toward the cornea by the movable portion of theindentation device during application of the fifth predetermined amountof force.

The differences are then preferably calculated between the first,second, and third distances, which differences are indicative of thevolume of intraocular fluid which left the eye and therefore are alsoindicative of the outflow facility. It is understood that the differencebetween the first and last distances may be used, and in this regard, itis not necessary to use the differences between all three distances. Infact, the difference between any two of the distances will suffice.

Although the relationship between the outflow facility and the detecteddifferences varies when the various parameters of the method and thedimensions of the indentation device change, the relationship for givenparameters and dimensions can be easily determined by known experimentaltechniques and/or using known Friedenwald Tables.

The method of the present invention is preferably carried out using anindenting surface which is three millimeters in diameter and a computerequipped with a data acquisition board. In particular, the computergenerates the predetermined forces via a digital-to-analog (D/A)converter connected to the current generating circuitry 32. The computerthen receives signals indicative of the first, second, and thirdpredetermined distances via an analog-to-digital (A/D) converter. Thesesignals are analyzed by the computer using the aforementionedrelationship between the differences in distance and the outflowfacility. Based on this analysis, the computer creates an output signalindicative of outflow facility. The output signal is preferably appliedto a display screen which, in turn, provides a visual indication ofoutflow facility.

Preferably, the method further comprises the steps of plotting thedifferences between the first, second, and third distances to a create agraph of the differences and comparing the resulting graph ofdifferences to that of a normal eye to determine if any irregularitiesin outflow facility are present. As indicated above, however, it isunderstood that the difference between the first and last distances maybe used, and in this regard, it is not necessary to use the differencesbetween all three distances. In fact, the difference between any two ofthe distances will suffice.

Preferably, the first predetermined frequency and second predeterminedfrequency are substantially equal and are approximately 20 Hertz.Generally, any frequencies up to 35 Hertz can be used, thoughfrequencies below 1 Hertz are generally less desirable because thestress relaxation of the eye's outer coats would contribute to changesin pressure and volume.

The fourth predetermined amount of force is preferably at least twicethe second predetermined amount of force, and the third predeterminedamount of force is preferably approximately half of the firstpredetermined amount of force. It is understood, however, that otherrelationships will suffice and that the present method is not limited tothe foregoing preferred relationships.

According to a preferred use of the method, the first predeterminedamount of force is between 0.01 Newton and 0.015 Newton; the secondpredetermined amount of force is between 0.005 Newton and 0.0075 Newtonthe third predetermined amount of force is between 0.005 Newton and0.0075 Newton; the fourth predetermined amount of force is between0.0075 Newton and 0.0125 Newton; the fifth predetermined amount of forceis between 0.0125 Newton and 0.025 Newton; the first predeterminedfrequency is between 1 Hertz and 35 Hertz; and the second predeterminedfrequency is also between 1 Hertz and 35 Hertz. The present method,however, is not limited to the foregoing preferred ranges.

Although the method of the present invention is preferably carried outusing the aforementioned device, it is understood that various othertonometers may be used. The method of the present invention therefore isnot limited in scope to its use in conjunction with the claimed systemand illustrated contact device.

ALTERNATIVE EMBODIMENTS OF THE CONTACT DEVICE

Although the foregoing description utilizes an embodiment of the contactdevice 2 which includes a flexible membrane 14 on the inside surface ofthe contact device 2, it is readily understood that the presentinvention is not limited to such an arrangement. Indeed, there are manyvariations of the contact device which fall well within the scope of thepresent invention.

The contact device 2, for example, may be manufactured with no flexiblemembrane, with the flexible membrane on the outside surface of thecontact device 2 (i.e., the side away from the cornea), with theflexible membrane on the inside surface of the contact device 2, or withthe flexible membrane on both sides of the contact device 2.

Also, the flexible membrane (s) 14 can be made to have an annular shape,thus permitting light to pass undistorted directly to the movablecentral piece 16 and the cornea for reflection thereby.

In addition, as illustrated in FIG. 12, the movable central piece 16 maybe formed with a similar annular shape so that a transparent centralportion thereof merely contains air. This way, light passing through theentire contact device 2 impinges directly on the cornea withoutundergoing any distortion due to the contact device 2.

Alternatively, the transparent central portion can be filled with atransparent solid material. Examples of such transparent solid materialsinclude polymethyl methacrylate, glass, hard acrylic, plastic polymers,and the like. According to a preferred arrangement, glass having anindex of refraction substantially greater than that of the cornea isutilized to enhance reflection of light by the cornea when the lightpasses through the contact device 2. Preferably, the index of refractionfor the glass is greater than 1.7, compared to the typical index ofrefraction of 1.37 associated with the cornea.

It is understood that the outer surface of the movable central piece 16may be coated with an anti-reflection layer in order to eliminateextraneous reflections from that surface which might otherwise interferewith operation of the alignment mechanism and the applanation detectingarrangement.

The interconnections of the various components of the contact device 2are also subject to modification without departing from the scope andspirit of the present invention. It is understood therefore that manyways exist for interconnecting or otherwise maintaining the workingrelationship between the movable central piece 16, the rigid annularmember 12, and the membranes 14.

When one or two flexible membranes 14 are used, for example, thesubstantially rigid annular member 12 can be attached to any one or bothof the flexible membrane(s) 14 using any known attachment techniques,such as gluing, heat-bonding, and the like. Alternatively, when twoflexible membranes 14 are used, the components may be interconnected orotherwise maintained in a working relationship, without having todirectly attach the flexible membrane 14 to the substantially rigidannular member 12. Instead, the substantially rigid annular member 12may be retained between the two flexible membranes 14 by bonding themembranes to one another about their peripheries while the rigid annularmember 12 is sandwiched between the membranes 14.

Although the movable central piece 16 may be attached to the flexiblemembrane(s) 14 by gluing, heat-bonding, and the like, it is understoodthat such attachment is not necessary. Instead, one or both of theflexible membranes 14 can be arranged so as to completely or partiallyblock the movable central piece 16 and prevent it from falling out ofthe hole in the substantially rigid annular member 12. When theaforementioned annular version of the flexible membranes 14 is used, asillustrated by way of example in FIG. 12, the diameter of the hole in atleast one of the annular flexible membranes 14 is preferably smallerthan that of the hole in the substantially rigid annular member 12 sothat a radially inner portion 14A of the annular flexible membrane 14overlaps with the movable central piece 16 and thereby prevents themovable central piece 16 from falling out of the hole in thesubstantially rigid annular member 21.

As illustrated in FIG. 13A, another way of keeping the movable centralpiece 16 from failing out of the hole in the substantially rigid annularmember 12 is to provide arms 16A which extend radially out from themovable central piece 16 and are slidably received in respective grooves16B. The grooves 16B are formed in the rigid annular member 12. Eachgroove 16B has a longitudinal dimension (vertical in FIG. 13) which isselectively chosen to restrict the range of movement of the movablecentral piece 16 to within predetermined limits. Although FIG. 13 showsan embodiment wherein the grooves are in the substantially rigid annularmember 12 and the arms extend out from the movable central piece 16, itis understood that an equally effective arrangement can be created byreversing the configuration such that the grooves are located in themovable central piece 16 and the arms extend radially in from thesubstantially rigid annular member 12.

Preferably, the grooves 16B include resilient elements, such asminiature springs, which bias the position of the movable central piece16 toward a desired starting position. In addition, the arms 16A mayinclude distally located miniature wheels which significantly reduce thefriction between the arms 16A and the walls of the grooves 16B.

FIG. 13B illustrates another way of keeping the movable central piece 16from falling out of the hole in the substantially rigid annular member12. In FIG. 13B, the substantially rigid annular member 12 is providedwith radially inwardly extending flaps 12F at the outer surface of theannular member 12. One of the aforementioned annular membranes 14 ispreferably disposed on the inner side of the substantially rigid annularmember 12. Preferably, a portion of the membrane 14 extends radiallyinwardly past the walls of the rigid annular member's hole. Thecombination of the annular membrane 14 and the flaps 12F keeps themovable central piece 16 from falling out of the hole in thesubstantially rigid annular member 12.

The flaps 12F may also be used to achieve or facilitate actuation of themovable central piece 16. In a magnetically actuated embodiment, forexample, the flaps 12F may be magnetized so that the flaps 12F moveinwardly in response to an externally applied magnetic field.

With reference to FIG. 14, an alternative embodiment of the contactdevice 2 is made using a soft contact lens material 12A having aprogressively decreasing thickness toward its outer circumference. Acylindrical hole 12B is formed in the soft contact lens material 12A.The hole 12B, however, does not extend entirely through the soft contactlens material 12A. Instead, the hole has a closed bottom defined by athin portion 12C of the soft contact lens material 12A. The movablecentral piece 16 is disposed slidably within the hole 12B, andpreferably, the thin portion 12C is no more than 0.2 millimeters thick,thereby allowing the movable central piece 16 to achieve applanation orindentation when moved against the closed bottom of the hole toward thecornea with very little interference from the thin portion 12C.

Preferably, a substantially rigid annular member 12D is inserted andsecured to the soft contact material 12A to define a more stable wallstructure circumferentially around the hole 12B. This, in turn, providesmore stability when the movable central piece 16 moves in the hole 12B.

Although the soft lens material 12A preferably comprises Hydrogel,silicone, flexible acrylic, or the like, it is understood that any othersuitable materials may be used. In addition, as indicated above, anycombination of flexible membranes may be added to the embodiment of FIG.14. Although the movable central piece 16 in FIG. 14 is illustrated asbeing annular, it is understood that any other shape may be utilized.For example, any of the previously described movable central pieces 16would suffice.

Similarly, the annular version of the movable central piece 16 may bemodified by adding a transparent bottom plate (not illustrated) whichdefines a flat transparent bottom surface of the movable central piece16. When modified in this manner, the movable central piece 16 wouldhave a generally cup-shaped appearance. Preferably, the flat transparentbottom surface is positioned toward the cornea to enhance the flatteningeffect of the movable central piece 16; however, it is understood thatthe transparent plate can be located on the outside surface of themovable central piece 16 if desired.

Although the movable central piece 16 and the hole in the substantiallyrigid annular member 12 (or the hole in the soft contact lens material12A) are illustrated as having complementary cylindrical shapes, it isunderstood that the complementary shapes are not limited to a cylinder,but rather can include any shape which permits sliding of the movablecentral piece 16 with respect to its surrounding structure.

It is also understood that the movable central piece 16 may be mounteddirectly onto the surface of a flexible membrane 14 without using asubstantially rigid annular member 12. Although such an arrangementdefines a working embodiment of the contact device 2, its stability,accuracy, and level of comfort are significantly reduced compared tothat of a similar embodiment utilizing the substantially rigid annularmember 12 with a progressively tapering periphery.

Although the illustrated embodiments of the movable central piece 16include generally flat outside surfaces with well defined lateral edges,it is understood that the present invention is not limited to sucharrangements. The present invention, for example, can include a movablecentral piece 16 with a rounded outer surface to enhance comfort and/orto coincide with the curvature of the outer surface of the substantiallyrigid annular member 12. The movable central piece can also be made tohave any combination of curved and flat surfaces defined at its innerand outer surfaces, the inner surface being the surface at the corneaand the outer surface being the surface directed generally away from thecornea.

With reference to FIG. 15, the movable central piece 16 may also includea centrally disposed projection 16P directed toward the cornea. Theprojection 16P is preferably created by extending the transparent solidmaterial in toward the cornea at the center of the movable central piece16.

ALTERNATIVE EMBODIMENT FOR MEASURING INTRAOCULAR PRESSURE BY APPLANATION

With reference to FIG. 16, an alternative embodiment of the system formeasuring intraocular pressure by applanation will now be described. Thealternative embodiment preferably utilizes the version of the contactdevice 2 which includes a transparent central portion.

According to the alternative embodiment, the schematically illustratedcoil 30 of the actuation apparatus includes an iron core 30A forenhancing the magnetic field produced by the coil 30. The iron core 30Apreferably has an axially extending bore hole 30B (approximately 6millimeters in diameter) which permits the passage of light through theiron core 30A and also permits mounting of two lenses L3 and L4 therein.

In order for the system to operate successfully, the strength of themagnetic force applied by the coil 30 on the movable central piece 16should be sufficient to applanate patients' corneas over at least thefull range of intraocular pressures encountered clinically (i.e. 5-50 mmHg). According to the illustrated alternative embodiment, intraocularpressures ranging from 1 to over 100 mm of mercury can be evaluatedusing the present invention. The forces necessary to applanate againstsuch intraocular pressures may be obtained with reasonablystraightforward designs and inexpensive materials as will bedemonstrated by the following calculations:

It is known that the force F exerted by an external magnetic field on asmall magnet equals the magnet's magnetic dipole moment m multiplied bythe gradient of the external field's magnetic induction vector "grad B"acting in the direction of the magnet's dipole moment.

    F=m*grad B                                                 (1)

The magnetic dipole moment m for the magnetic version of the movablecentral piece 16 can be determined using the following formula:

    m=(B*V)/u.sub.0                                            (2)

where B is the magnetic induction vector just at the surface of one ofthe poles of the movable central piece 16, V is its volume, and u₀ isthe magnetic permeability of free space which has a value of 12.57 *10⁻⁷ Henry/meter.

A typical value of B for magnetized Alnico movable central pieces 16 is0.5 Tesla. If the movable central piece 16 has a thickness of 1 mm, adiameter of 5 mm, and 50% of its initial volume is machined away, itsvolume V=9.8 cubic millimeters (9.8 * 10⁻⁹ cubic meters. Substitutingthese values into Equation 2 yields the value for the movable centralpiece's magnetic dipole moment, namely, m=0.00390 Amp* (Meter)².

Using the foregoing calculations, the specifications of the actuationapparatus can be determined. The magnetic field gradient "grad B" is afunction of the distance x measured from the front face of the actuationapparatus and may be calculated as follows: ##EQU1## where X is themagnetic susceptibility of the iron core, N is the number of turns inthe coil's wire, I is the electric current carried by the wire, L is thelength of the coil 30, and RAD is the radius of the coil 30.

The preferred values for these parameters in the alternative embodimentare: X=500, N=200, I=1.0 Amp, L=0.05 meters, and RAD=0.025 meters. It isunderstood, however, that the present invention is not limited to thesepreferred parameters. As usual, u₀ =12.57 * 10⁻⁷ Henry/meter.

The force F exerted by the magnetic actuation apparatus on the movablecentral piece 16 is found from Equation 1 using the aforementionedpreferred values as parameters in Equation 3, and the above result form=0.00390 Amp* (Meter)2. A plot of F as a function of the distance xseparating the movable central piece 16 from the pole of the magneticactuation apparatus appears as FIG. 16A.

Since a patient's cornea 4, when covered by the contact device 2 whichholds the movable central piece 16, can be placed conveniently at adistance x32 2.5 cm (0.025 m) from the actuation apparatus, it is notedfrom FIG. 16A that the magnetic actuation force is approximately F=0.063Newtons.

This force is then compared to F_(required) which is the force actuallyneeded to applanate a cornea 4 over a typical applanation area when theintraocular pressure is as high as 50 mm Hg. In Goldman tonometry, thediameter of the applanated area is approximately 3.1 mm and thereforethe typical applanated AREA will equal 7.55 mm². The typical maximumpressure of 50 mm Hg can be converted to metric form, yielding apressure of 0.00666 Newtons/mm². The value of F_(required) then can bedetermined using the following equation:

    F.sub.required =PRESSURE*AREA                              (4)

After mathematical substitution, F_(required) =0.050 Newtons. Comparingthe calculated magnetic actuation force F to the force requiredF_(required), it becomes clear that F_(required) is less than theavailable magnetic driving force F. Therefore, the maximum force neededto applanate the cornea 4 for intraocular pressure determinations iseasily achieved using the actuation apparatus and movable central piece16 of the present invention.

It is understood that, if a greater force becomes necessary for whateverreason (e.g, to provide more distance between the contact device 2 andthe actuation apparatus), the various parameters can be manipulatedand/or the current in the coil 30 can be increased to achieve asatisfactory arrangement.

In order for the actuation apparatus to properly actuate the movablecentral piece 16 in a practical way, the magnetic actuation force (andthe associated magnetic field) should increase from zero, reach amaximum in about 0.01 sec., and then return back to zero inapproximately another 0.01 sec. The power supply to the actuationapparatus therefore preferably includes circuitry and a power sourcecapable of driving a "current pulse" of peak magnitude in the 1 ampererange through a fairly large inductor (i.e. the coil 30).

For "single-pulse" operation, a DC-voltage power supply can be used tocharge a capacitor C through a charging resistor. One side of thecapacitor is grounded while the other side ("high" side) may be at a 50volt DC potential. The "high" side of the capacitor can be connected viaa high current-carrying switch to a "discharge circuit" consisting ofthe coil 30 and a damping resistor R This arrangement yields an R-L-Cseries circuit similar to that which is conventionally used to generatelarge pulses of electrical current for such applications as obtaininglarge pulsed magnetic fields and operating pulsed laser power systems.By appropriately choosing the values of the electrical components andthe initial voltage of the capacitor, a "current pulse" of the kinddescribed above can be generated and supplied to the coil 30 to therebyoperate the actuation apparatus.

It is understood, however, that the mere application of a current pulseof the kind described above to a large inductor, such as the coil 30,will not necessarily yield a zero magnetic field after the current pulsehas ended. Instead, there is usually an undesirable residual magneticfield from the iron-core 30A even though no current is flowing in thecoil 30. This residual field is caused by magnetic hysteresis and wouldtend to produce a magnetic force on the movable central piece 16 whensuch a force is not wanted.

Therefore, the alternative embodiment preferably includes means forzeroing the magnetic field outside the actuation apparatus afteroperation thereof Such zeroing can be provided by a demagnetizingcircuit connected to the iron-core 30A.

Methods for demagnetizing an iron-core are generally known and are easyto implement. It can be done, for example, by reversing the current inthe coil repeatedly while decreasing its magnitude. The easiest way todo this is by using a step-down transformer where the input is asinusoidal voltage at 60 Hz which starts at a "line voltage" of 110 VACand is gradually dampened to zero volts, and where the output of thetransformer is connected to the coil 30.

The actuation apparatus therefore may include two power circuits,namely, a "single pulse" current source used for conducting applanationmeasurements and a "demagnetization circuit" for zeroing the magneticfield of the coil 30 immediately after each applanation measurement.

As illustrated in FIGS. 16 and more specifically in FIG. 17, thealternative embodiment used for applanation also includes an alternativeoptical alignment system. Alignment is very important because, asindicated by the graph of FIG. 16A, the force exerted by the actuationapparatus on the movable central piece 16 depends very much on theirrelative positions. In addition to the movable central piece's axiallocation with respect to the actuation apparatus (x-direction), themagnetic force exerted on the movable central piece 16 also depends onits lateral (y-direction) and vertical (z-direction) positions, as wellas on its orientation (tip and tilt) with respect to the central axis ofthe actuation apparatus.

Considering the variation of force F with axial distance x shown in FIG.16A, it is clear that the movable central piece 16 should be positionedin the x-direction with an accuracy of about +/-1 mm for reliablemeasurements. Similarly, since the diameter of the coil 30 is preferably50 mm, the location of the movable central piece 16 with respect to they and z directions (i.e. perpendicular to the longitudinal axis of thecoil 30) should be maintained to within +/-2 mm (a region where themagnetic field is fairly constant) of the coil's longitudinal axis.

Finally, since the force on the movable central piece 16 depends on thecosine of the angle between the coil's longitudinal axis and the tip ortilt angle of the movable central piece 16, it is important that therange of the patient's gaze with respect to the coil's longitudinal axisbe maintained within about +/-2 degrees for reliable measurements.

In order to satisfy the foregoing criteria, the alternative opticalalignment system facilitates precise alignment of the patient's cornealvertex (situated centrally behind the movable central piece 16) with thecoil's longitudinal axis, which precise alignment can be achievedindependently by a patient without the assistance of a trained medicaltechnician or health care professional.

The alternative optical alignment system functions according to howlight reflects and refracts at the corneal surface. For the sake ofsimplicity, the following description of the alternative opticalalignment system and FIGS. 16 and 17 does not refer specifically to theeffects of the movable central piece's transparent central portion onthe operation of the optical system, primarily because the transparentcentral portion of the movable central piece 16 is preferably arrangedso as not to affect the behavior of optical rays passing through themovable central piece 16.

Also, for the sake of simplicity, FIG. 17 does not show the iron core30A and its associated bore 30B, though it is understood that thealignment beam (described hereinafter) passes through the bored hole 30Band that the lenses L3 and L4 are mounted within the bored hole 30B.

As illustrated in FIG. 16, a point-like source 350 of light such as anLED is located at the focal plane of a positive (i.e., convergent) lensL1. The positive lens L1 is arranged so as to collimate a beam of lightfrom the source 350. The collimated beam passes through a beam splitterBS1 and a transmitted beam of the collimated beam continues through thebeam splitter BS1 to a positive lens L2. The positive lens L2 focusesthe transmitted beam to a point within lens L3 located at the focalplane of a lens L4. The light rays passing through L4 are collimatedonce again and enter the patient's eye where they are focused on theretina 5. The transmitted beam is therefore perceived by the patient asa point-like light.

Some of the rays which reach the eye are reflected from the cornealsurface in a divergent manner due to the cornea's preapplanationcurvature, as shown in FIG. 18, and are returned back to the patient'seye by a partially mirrored planar surface of the lens L4. These raysare perceived by the patient as an image of the corneal reflection whichguides the patient during alignment of his/her eye in the instrument aswill be described hereinafter.

Those rays which are reflected by the convex cornea 4 and pass fromright-to-left through the lens L4 are made somewhat more convergent bythe lens L4. From the perspective of lens L3, these rays appear to comefrom a virtual point object located at the focal point. Therefore, afterpassing through L3, the rays are once again collimated and enter thelens L2 which focuses the rays to a point on the surface of the beamsplitter BS1. The beam splitter BS1 is tilted at 45 degrees andconsequently deflects the rays toward a lens L5 which, in turn,collimates the rays. These rays then strike the surface of a tiltedreflecting beam splitter BS2. The collimated rays reflected from thebeam splitter BS2 enter lens L6 which focuses them onto the smallaperture of a silicon photodiode which functions as an alignment sensorD1.

Therefore, when the curved cornea 4 is properly aligned, an electriccurrent is produced by the alignment sensor D1. The alignment system isvery sensitive because it is a confocal arrangement (i.e., the pointimage of the alignment light due to the corneal reflection--Purkinjeimage--in its fiducial position is conjugate to the smalllight-sensitive aperture of the silicon photodiode). In this manner, anelectrical current is obtained from the alignment sensor only when thecornea 4 is properly aligned with respect to the lens L4 which, in turn,is preferably mounted at the end of the magnetic actuation apparatus.The focal lengths of all the lenses shown in FIG. 17 are preferably 50mm except for the lens L3 which preferably has a focal length of 100 MM.

An electrical circuit capable of operating the alignment sensor D1 isstraight-forward to design and build. The silicon photodiode operateswithout any bias voltage ("photovoltaic mode") thus minimizing inherentdetector noise. In this mode, a voltage signal, which corresponds to thelight level on the silicon surface, appears across a small resistorspanning the diode's terminals. Ordinarily this voltage signal is toosmall for display or subsequent processing; however, it can be amplifiedmany orders of magnitude using a simple transimpedance amplifiercircuit. Preferably, the alignment sensor D1 is utilized in conjunctionwith such an amplified photodiode circuit.

Preferably, the circuitry connected to the alignment sensor D1 isarranged so as to automatically activate the actuation apparatusimmediately upon detecting via the sensor D1 the existence of properalignment. If, however, the output from the alignment sensor D1indicates that the eye is not properly aligned, the circuitry preferablyprevents activation of the actuation apparatus. In this way, thealignment sensor D1, not the patient, determines when the actuationapparatus will be operated.

As indicated above, the optical alignment system preferably includes anarrangement for guiding the patient during alignment of his/her eye inthe instrument. Such arrangements are illustrated, by way of example, inFIGS. 18 and 19.

The arrangement illustrated in FIG. 18 allows a patient to preciselyposition his/her eye translationally in all x-y-z directions. Inparticular, the lens L4 is made to include a piano surface, the planosurface being made partially reflective so that a patient is able to seea magnified image of his/her pupil with a bright point source of lightlocated somewhere near the center of the iris. This point source imageis due to the reflection of the incoming alignment beam from the curvedcorneal surface (called the first Purkinje image) and its subsequentreflection from the mirrored or partially reflecting piano surface ofthe lens L4. Preferably, the lens L4 makes the reflected rays parallelas they return to the eye which focuses them onto the retina 5.

Although FIG. 18 shows the eye well aligned so that the rays are focusedat a central location on the surface of the retina 5, it is understoodthat movements of the eye toward or away (x-direction) from the lens L4will blur the image of the corneal reflection, and that movements of theeye in either the y or z direction will tend to displace the cornealreflection image either to the right/left or up/down.

The patient therefore performs an alignment operation by gazing directlyat the alignment light and moving his/her eye slowly in three dimensionsuntil the point image of the corneal reflection is as sharp as possible(x-positioning) and merges with the point image of the alignment light(y & z positioning) which passes straight through the cornea 4.

As illustrated in FIG. 19, the lens L4 need not have a partiallyreflective portion if the act of merely establishing a proper directionof gaze provides sufficient alignment.

Once alignment is achieved, a logic signal from the optical alignmentsystem activates the "pulse circuit" which, in turn, powers theactuation apparatus. After the actuation apparatus is activated, themagnetic field at the patient's cornea increases steadily for a timeperiod of about 0.01 sec. The effect of this increasing field is toapply a steadily increasing force to the movable central piece 16resting on the cornea which, in turn, causes the cornea 4 to flattenincreasingly over time. Since the size of the applanation area isproportional to the force on the movable central piece 16 (andPressure=Force/Area), the intraocular pressure (IOP) is found bydetermining the ratio of the force to the area applanated by the force.

In order to detect the applanated area and provide an electrical signalindicative of the size of the applanated area, the alternativeembodiment includes an applanation sensor D2. The rays that arereflected from the applanated corneal surface are reflected in agenerally parallel manner by virtue of the flat surface presented by theapplanated cornea 4. As the rays pass from right-to-left through thelens L4, they are focused within the lens L3 which, in turn, is in thefocal plane of the lens L2. Consequently, after passing through the lensL2, the rays are once again collimated and impinge on the surface ofbeam splitter BS1. Since the beam splitter BS1 is tilted at 45 degrees,the beam splitter BS1 deflects these collimated rays toward the lens L5which focuses the rays to a point at the center of beam splitter BS2.The beam splitter BS2 has a small transparent portion or hole in itscenter which allows the direct passage of the rays on to the lens L7(focal length of preferably 50 mm). The lens L7 pertains to anapplanation sensing arm of the alternative embodiment.

The focal spot on the beam splitter BS2 is in the focal plane of thelens L7. Consequently, the rays emerging from the lens L7 are once againcollimated. These collimated rays impinge on the mirror M1, preferablyat a 45 degree angle, and are deflected toward a positive lens L8 (focallength of 50 mm) which focuses the rays onto the small aperture of asilicon photodiode which defines the applanation sensor D2.

It is understood that rays which impinge upon the cornea 4 slightly offcenter tend to be reflected away from the lens L4 when the cornea'scurvature remains undisturbed. However, as applanation progresses andthe cornea becomes increasingly flat, more of these rays are reflectedback into the lens L4. The intensity of light on the applanation sensorD2 therefore increases, and as a result, an electric current isgenerated by the applanation sensor D2, which electric current isproportional to the degree of applanation.

Preferably, the electrical circuit utilized by the applanation sensor D2is identical or similar to that used by the alignment sensor D1

The electric signal indicative of the area of applanation can then becombined with signals indicative of the time it takes to achieve suchapplanation and/or the amount of current (which, in turn, corresponds tothe applied force) used to achieve the applanation, and this combinationof information can be used to determine the intraocular pressure usingthe equation Pressure=Force/Area.

The following are preferred operational steps for the actuationapparatus during a measurement cycle:

1) While the actuation apparatus is OFF, there is no magnetic fieldbeing directed toward the contact device 2.

2) When the actuation apparatus is turned ON, the magnetic fieldinitially remains at zero.

3) Once the patient is in position, the patient starts to align his/hereye with the actuation apparatus. Until the eye is properly aligned, themagnetic field remains zero.

4) When the eye is properly aligned (as automatically sensed by theoptical alignment Sensor), the magnetic field (driven by a steadilyincreasing electric current) starts to increase from zero.

5) During the time period of the current increase (approximately 0.01sec.), the force on the movable central piece also increases steadily.

6) In response to the increasing force on the movable central piece, thesurface area of the cornea adjacent to the movable central piece isincreasingly flattened.

7) Light from the flattened surface area of the cornea is reflectedtoward the detecting arrangement which detects when a predeterminedamount of applanation has been achieved. Since the amount of lightreflected straight back from the cornea is proportional to the size ofthe flattened surface area, it is possible to determine exactly when thepredetermined amount of applanation has been achieved, preferably acircular area of diameter 3.1 mm, of the cornea. It is understood,however, that any diameter ranging from 0.10 mm to 10 mm can beutilized.

8) The time required to achieve applanation of the particular surfacearea (i.e, the predetermined amount of applanation) is detected by atiming circuit which is part of the applanation detecting arrangement.Based on prior calibration and a resulting conversion table, this timeis converted to an indication of intraocular pressure. The longer thetime required to applanate a specific area, the higher the intraocularpressure, and vice versa.

9) After the predetermined amount of applanation is achieved, themagnetic field is turned OFF.

10) The intraocular pressure is then displayed by a readout meter, andall circuits are preferably turned completely OFF for a period of 15seconds so that the automatic measurement cycle will not be immediatelyrepeated if the patient's eye remains aligned. It is understood,however, that the circuits may remain ON and that a continuousmeasurement of intraocular pressure may be achieved by creating anautomatic measurement cycle. The data provided by this automaticmeasurement cycle then may be used to calculate blood flow.

11) If the main power supply has not been turned OFF, all circuits areturned back ON after 15 seconds and thus become ready for the nextmeasurement.

Although there are several methods for calibrating the various elementsof the system for measuring intraocular pressure by applanation, thefollowing are illustrative examples of how such calibration can beachieved:

Initially, after manufacturing the various components, each component istested to ensure the component operates properly. This preferablyincludes verifying that there is free piston-like movement (no twisting)of the movable central piece in the contact device; verifying thestructural integrity of the contact device during routine handling;evaluating the magnetic field at the surface of the movable centralpiece in order to determine its magnetic dipole moment (when magneticactuation is utilized); verifying that the electrical current pulsewhich creates the magnetic field that actuates the magneticallyresponsive element of the movable central piece, has an appropriate peakmagnitude and duration, and ensuring that there is no "ringing";verifying the efficacy of the "demagnetization circuit" at removing anyresidual magnetization in the iron-core of the actuation apparatus afterit has been pulsed; measuring the magnetic field as a function of timealong and near the longitudinal axis of the coil where the movablecentral piece will eventually be placed; determining and plotting grad Bas a function of time at several x-locations (i.e., at several distancesfrom the coil); and positioning the magnetic central piece (contactdevice) at several x-locations along the coil's longitudinal axis anddetermining the force F acting on it as a function of time duringpulsed-operation of the actuation apparatus.

Next, the optical alignment system is tested for proper operation. Whenthe optical alignment system comprises the arrangement illustrated inFIGS. 16 and 17, for example, the following testing and calibrationprocedure may be used:

a) First, a convex glass surface (one face of a lens) having a radius ofcurvature approximately the same as that of the cornea is used tosimulate the cornea and its surface reflection. Preferably, this glasssurface is placed in a micrometer-adjusted mounting arrangement alongthe longitudinal axis of the coil. The micrometer-adjusted mountingarrangement permits rotation about two axes (tip & tilt) and translationin three-dimensional x-y-z space.

b) With the detector D1 connected to a voltage or current meter, theconvex glass surface located at its design distance of 25 mm from lensL4 will be perfectly aligned (tip/tilt/x/y/z) by maximizing the outputsignal at the read-out meter.

c) After perfect alignment is achieved, the alignment detectionarrangement is "detuned" for each of the positional degrees of freedom(tip/tilt/x/y/z) and curves are plotted for each degree of freedom tothereby define the system's sensitivity to alignment.

d) The sensitivity to alignment will be compared to the desiredtolerances in the reproducibility of measurements and also can be basedon the variance of the magnetic force on the movable central piece as afunction of position.

e) Thereafter, the sensitivity of the alignment system can be changed asneeded by such procedures as changing the size of the aperture in thesilicon photodiode which functions as the alignment sensor D1. and/orchanging an aperture stop at lens L4.

Next, the detection arrangement is tested for proper operation. When thedetection arrangement comprises the optical detection arrangementillustrated in FIG. 16, for example, the following testing andcalibration procedure may be used:

a) A flat glass surface (e.g., one face of a short polished rod) with adiameter of preferably 4-5 mm is used to simulate the applanated corneaand its surface reflection.

b) A black, opaque aperture defining mechanism (which defines clearinner apertures with diameters ranging from 0.5 to 4 mm and which has anouter diameter the same as that of the rod) is arranged so as topartially cover the face of the rod, thus simulating various stages ofapplanation.

c) The flat surfaced rod is placed in a mount along the longitudinalaxis of the coil in a micrometer-adjusted mounting arrangement that canrotate about two axes (tip & tilt) and translate in three-dimensionalx-y-z space.

d) The applanation sensor D2 is then connected to a voltage or currentmeter, while the rod remains located at its design distance of 25 mmfrom the lens L4 where it is perfectly aligned (tip/tilt/x/y/z) bymaximizing the output signal from the applanation sensor D2. Alignment,in this case, is not sensitive to x-axis positioning.

e) After perfect alignment is achieved, the alignment is "detuned" foreach of the positional degrees of freedom (tip/tilt/x/y/z) and curvesare plotted for each degree of freedom thus defining the system'ssensitivity to alignment. Data of this kind is obtained for thevariously sized apertures (i.e. different degrees of applanation) at theface of the rod.

f) The sensitivity to alignment is then compared to the tolerancesrequired for reproducing applanation measurements which depends, inpart, on the results obtained in the aforementioned testing andcalibration method associated with the alignment apparatus.

g) The sensitivity of the applanation detecting arrangement is thenchanged as needed by such procedures as changing the size of theaperture in front of the applanation sensor D2 and/or changing theaperture stop (small hole) at the beam splitter BS2.

Further calibration and in-vitro measurements can be carried out asfollows: After the aforementioned calibration and testing procedureshave been carried out on the individual subassemblies, all parts can becombined and the system tested as an integrated unit. For this purpose,ten enucleated animal eyes and ten enucleated human eyes are measured intwo separate series. The procedures for both eye types are the same. Theeyes are mounted in non-magnetic holders, each having a central openingwhich exposes the cornea and part of the sclera. A 23 gauge needleattached to a short piece of polyethylene tubing is then inserted behindthe limbus through the sclera and ciliary body and advanced so that thetip passes between the lens and iris. Side ports are drilled in thecannulas about 2 mm from the tip to help avoid blockage of the cannulaby the iris or lens. This cannula is attached to a pressure transducerwith an appropriate display element. A normal saline reservoir ofadjustable height is also connected to the pressure transducer tubingsystem. The hydrostatic pressure applied to the eye by this reservoir isadjustable between 0 and 50 mm Hg, and intraocular pressure over thisrange can be measured directly with the pressure transducer.

In order to verify that the foregoing equipment is properly set up foreach new eye, a standard Goldman applanation tonometer can be used toindependently measure the eye's intraocular pressure at a single heightof the reservoir. The intraocular value measured using the Goldmansystem is then compared to a simultaneously determined intraocularpressure measured by the pressure transducer. Any problems encounteredwith the equipment can be corrected if the two measurements aresignificantly different.

The reservoir is used to change in 5 mm Hg sequential steps theintraocular pressure of each eye over a range of pressures from 5 to 50mm Hg. At each of the pressures, a measurement is taken using the systemof the present invention. Each measurement taken by the presentinvention consists of recording three separate time-varying signals overthe time duration of the pulsed magnetic field. The three signalsare: 1) the current flowing in the coil of the actuation apparatus as afunction of time, labelled I (t), 2) the voltage signal as a function oftime from the applanation detector D2, labelled APPLN (t), and 3) thevoltage signal as a function of time from the alignment sensor D1,labelled ALIGN (t). The three signals, associated with each measurement,are then acquired and stored in a computer equipped with a multi-input"data acquisition and processing" board and related software.

The computer allows many things to be done with the data including: 1)recording and storing many signals for subsequent retrieval, 2)displaying graphs of the signals versus time, 3) numerical processingand analyses in any way that is desired, 4) plotting final results, 5)applying statistical analyses to groups of data, and 6) labeling thedata (e.g. tagging a measurement set with its associated intraocularpressure).

The relationship between the three time-varying signals and intraocularpressure are as follows:

1. I(t) is an independent input signal which is consistently applied ascurrent pulse from the power supply which activates the actuationapparatus. This signal I (t) is essentially constant from onemeasurement to another except for minor shot-to-shot variations. I (t)is a "reference" waveform against which the other waveforms, APPLN (t)and ALIGN (t) are compared as discussed further below.

2. APPLN(t) is a dependent output signal. APPLN(t) has a value of zerowhen I(t) is zero (i.e. at the very beginning of the current pulse inthe coil of the actuation apparatus. The reason for this is that whenI=0, there is no magnetic field and, consequently. no applanation forceon the movable central piece. As I (t) increases, so does the extent ofapplanation and, correspondingly, so does APPLN(t). It is important tonote that the rate at which APPLN(t) increases with increasing I(t)depends on the eye's intraocular pressure. Since eyes with lowintraocular pressures applanate more easily than eyes with highintraocular pressures in response to an applanation force, it isunderstood that APPLN(t) increases more rapidly for an eye having a lowintraocular pressure than it does for an eye having a high intraocularpressure. Thus, APPLN (t) increases from zero at a rate that isinversely proportional to the intraocular pressure until it reaches amaximum value when full applanation is achieved.

3. ALIGN(t) is also a dependent output signal. Assuming an eye isaligned in the setup, the signal ALIGN(t) starts at some maximum valuewhen I(t) is zero (i.e. at the very beginning of the current pulse tothe coil of the actuation apparatus). The reason for this is that whenI=0, there is no magnetic field and, consequently, no force on themovable central piece which would otherwise tend to alter the cornea'scurvature. Since corneal reflection is what gives rise to the alignmentsignal, as I(t) increases causing applanation (and, correspondingly, adecrease in the extent of corneal curvature), the signal ALIGN (t)decreases until it reaches zero at full applanation. It is important tonote that the rate at which ALIGN (t) decreases with increasing I(t)depends on the eye's intraocular pressure. Since extraocular pressureapplanate more easily than eyes with high intraocular pressure, it isunderstood that ALIGN (t) decreases more rapidly for an eye having a lowintraocular pressure than for an eye having a high intraocular pressure.Thus, ALIGN(t) decreases from some maximum value at a rate that isinversely proportional to the intraocular pressure until it reaches zerowhen full applanation is achieved.

From the foregoing, it is clear that the rate of change of both outputsignals, APPLN and ALIGN, in relation to the input signal I is inverselyproportional to the intraocular pressure. Therefore, the measurement ofintraocular pressure using the present invention may depend ondetermining the SLOPE of the "APPLN versus I" measurement data (also,although probably with less certainty, the slope of the "ALIGN versus I"measurement data).

For the sake of brevity, the following description is limited to the"APPLN versus I" data; however, it is understood that the "ALIGN versusI" data can be processed in a similar manner.

Plots of "APPLN versus I" can be displayed on the computer monitor forthe various measurements (all the different intraocular pressures foreach and every eye) and regression analysis (and other data reductionalgorithms) can be employed in order to obtain the "best fit" SLOPE foreach measurement. Time can be spent in order to optimize this datareduction procedure. The end result of a series of pressure measurementsat different intraocular pressures on an eye (determined by theaforementioned pressure transducer) will be a corresponding series ofSLOPE's (determined by the system of the present invention).

Next, a single plot is prepared for each eye showing SLOPE versusintraocular pressure data points as well as a best fitting curve throughthe data. Ideally, all curves for the 10 pig eyes are perfectlycoincident--with the same being true for the curves obtained for the 10human eyes. If the ideal is realized, any of the curves can be utilized(since they all are the same) as a CALIBRATION for the presentinvention. In practice, however, the ideal is probably not realized.

Therefore, all of the SLOPE versus intraocular pressure data for the 10pig eyes is superimposed on a single plot (likewise for the SLOPE versusintraocular pressure data for the 10 human eyes). Such superimposinggenerally yields an "averaged" CALIBRATION curve, and also indication ofthe reliability associated with the CALIBRATION.

Next, the data in the single plots can be analyzed statistically (onefor pig eyes and one for human eyes) which, in turn, shows a compositeof all the SLOPE versus intraocular pressure data. From the statisticalanalysis, it is possible to obtain: 1) an averaged CALIBRATION curve forthe present invention from which one can obtain the "most likelyintraocular pressure" associated with a measured SLOPE value, 2) theStandard Deviation (or Variance) associated with any intraocularpressure determination made using the present invention, essentially thepresent invention's expected "ability" to replicate measurements, and 3)the "reliability" or "accuracy" of the present invention's CALIBRATIONcurve which is found from a "standard-error-of-the mean" analysis of thedata.

In addition to data obtained with the eyes aligned, it is also possibleto investigate the sensitivity of intraocular pressure measurements madeusing the present invention, to translational and rotationalmisalignment.

ALTERNATIVE EMBODIMENT FOR MEASURING INTRAOCULAR PRESSURE BY INDENTATION

With reference to FIGS. 20A and 20B, an alternative embodiment formeasuring intraocular pressure by indentation will now be described.

The alternative embodiment includes an indentation distance detectionarrangement and contact device. The contact device has a movable centralpiece 16 of which only the outside surface is illustrated in FIGS. 20Aand 20B. The outside surface of the movable central piece 16 is at leastpartially reflective.

The indentation distance detection arrangement includes two converginglenses L1 and L2; a beam splitter BS1; a light source LS for emitting abeam of light having a width w; and a light detector LD responsive tothe diameter of a reflected beam impinging on a surface thereof.

FIG. 20A illustrates the alternative embodiment prior to actuation ofthe movable central piece 16. Prior to actuation, the patient is alignedwith the indentation distance detection arrangement so that the outersurface of the movable central piece 16 is located at the focal point ofthe converging lens L2. When the movable central piece 16 is so located,the beam of light from the light source LS strikes the beam splitter BSand is deflected through the converging lens L1 to impinge as a point onthe reflective outer surface of the movable central piece 16. Thereflective outer surface of the movable central piece 16 then reflectsthis beam of light back through the converging lens L1, through the beamsplitter BS, and then through the converging lens L2 to strike a surfaceof the light detector LD. Preferably, the light detector LD is locatedat the focal point of the converging lens L2 so that the reflected beamimpinges on a surface of the light detector LD as a point of virtuallyzero diameter when the outer surface of the movable central pieceremains at the focal point of the converging lens L1.

Preferably, the indentation distance detection arrangement is connectedto a display device so as to generate an indication of zero displacementwhen the outer surface of the movable central piece 16 has yet to bedisplaced, as shown in FIG. 20A.

By subsequently actuating the movable central piece 16 using anactuating device (preferably, similar to the actuating devices describedabove), the outer surface of the movable central piece 16 movesprogressively away from the focal point of the converging lens L1, asillustrated in FIG. 20B. As a result, the light beam impinging on thereflective outer surface of the movable central piece 16 has aprogressively increasing diameter. This progressive increase in diameteris proportional to the displacement from the focal point of theconverging lens L1. The resulting reflected beam therefore has adiameter proportional to the displacement and passes back through theconverging lens L1, through the beam splitter BS, through the converginglens C2 and then strikes the surface of the light detector LD with adiameter proportional to the displacement of the movable central piece16. Since the light detector LD is responsive, as indicated above, tothe diameter of the reflected light beam, any displacement of themovable central piece 16 causes a proportional change in output from thelight detector LD.

Preferably, the light detector LD is a photoelectric converter connectedto the aforementioned display device and capable of providing an outputvoltage proportional to the diameter of the reflected light beamimpinging upon the light detector LD. The display device thereforeprovides a visual indication of displacement based on the output voltagefrom the light detector LD.

Alternatively, the output from the light detector LD may be connected toan arrangement, as described above, for providing an indication ofintraocular pressure based on the displacement of the movable centralpiece 16.

ADDITIONAL CAPABILITIES

Generally, the present apparatus and method makes it possible toevaluate intraocular pressure, as indicated above, as well as ocularrigidity, eye hydrodynamics such as outflow facility and inflow rate ofeye fluid, eye hemodynamics such as the pressure in the episcleral veinsand the pulsatile ocular blood flow, and has also the ability toartificially increase intraocular pressure, as well as the continuousrecording of intraocular pressure.

With regard to the measurement of intraocular pressure by applanation,the foregoing description sets forth several techniques foraccomplishing such measurement, including a variable force techniquewherein the force applied against the cornea varies with time. It isunderstood, however, that a variable area method can also beimplemented.

The apparatus can evaluate the amount of area applanated by a knownforce. The pressure is calculated by dividing the force by the amount ofarea that is applanated. The amount of area applanated is determinedusing the optical means and/or filters previously described.

A force equivalent to placing 5 gram of weight on the cornea, forexample, will applanate a first area if the pressure is 30 mmHg, asecond area if the pressure is 20 mmHg, a third area if the pressure is15 mmHg and so on. The area applanated is therefore indicative ofintraocular pressure.

Alternatively, intraocular pressure can be measured using a non-rigidinterface and general applanation techniques. In this embodiment, aflexible central piece enclosed by the magnet of the movable centralpiece is used and the transparent part of the movable central piece actslike a micro-balloon. This method is based on the principle that theinterface between two spherical balloons of unequal radius will be flatif the pressures in the two balloons are equal. The central piece withthe balloon is pressed against the eye until the eye/central pieceinterface is planar as determined by the aforementioned optical means.

Also, with regard to the previously described arrangement which measuresintraocular pressure by indentation, an alternative method can beimplemented with such an embodiment wherein the apparatus measures theforce required to indent the cornea by a predetermined amount. Thisamount of indentation is determined by optical means as previouslydescribed. The movable central piece is pressed against the cornea toindent the cornea, for example, 0.5 mm (though it is understood thatvirtually any other depth can be used). Achievement of the predetermineddepth is detected by the previously described optical means and filters.According to tables, the intraocular pressure can be determinedthereafter from the force.

Yet another technique which the present invention facilitates use of isthe ballistic principle. According to the ballistic principle, aparameter of a collision between the known mass of the movable centralpiece and the cornea is measured. This measured parameter is thenrelated theoretically or experimentally to the intraocular pressure. Thefollowing are exemplary parameters:

Impact Acceleration

The movable central piece is directed at the cornea at a well definedvelocity. It collides with the cornea and, after a certain time ofcontact, bounces back. The time-velocity relationships during and afterimpact can be studied. The applanating central piece may have a springconnecting to the rigid annular member of the contact device. If thecorneal surface is hard, the impact time will be short. Likewise, if thecorneal surface is soft the impact time will be longer. Optical sensorscan detect optically the duration of impact and how long it takes forthe movable central piece to return to its original position.

Impact Duration

Intraocular pressure may also be estimated by measuring the duration ofcontact of a spring driven movable central piece with the eye. Theamount of time that the cornea remains flattened can be evaluated by thepreviously described optical means.

Rebound Velocity

The distance traveled per unit of time after bouncing is also indicativeof the rebound energy and this energy is proportional to intraocularpressure.

Vibration Principle

The intraocular pressure also can be estimated by measuring thefrequency of a vibrating element in contact with the contact device andthe resulting changes in light reflection are related to the pressure inthe eye.

Time

The apparatus of the present invention can also be used, as indicatedabove, to measure the time that it takes to applanate the cornea. Theharder the cornea, the higher the intraocular pressure and thus thelonger it takes to deform the cornea. On the other hand, the softer thecornea, the lower the intraocular pressure and thus the shorter it takesto deform the cornea. Thus, the amount of time that it takes to deformthe cornea is proportional to the intraocular pressure.

Additional uses and capabilities of the present invention relate toalternative methods of measuring outflow facility (tonography). Thesealternative methods include the use of conventional indentationtechniques, constant depth indentation techniques, constant pressureindentation techniques, constant pressure applanation techniques,constant area applanation techniques, and constant force applanationtechniques.

1. Conventional Indentation

When conventional indentation techniques are utilized, the movablecentral piece of the present invention is used to indent the cornea andthereby artificially increase the intraocular pressure. This artificialincrease in intraocular pressure forces fluid out of the eye morerapidly than normal. As fluid leaves the eye, the pressure graduallyreturns to its original level. The rate at which the intraocularpressure falls depends on how well the eye's drainage system isfunctioning. The drop in pressure as a function of time is used tocalculated the C value or coefficient of outflow facility. The C valueis indicative of the degree to which a change in intraocular pressurewill cause a change in the rate of fluid outflow. This, in turn, isindicative of the resistance to outflow provided by the eye's drainagesystem. The various procedures for determining outflow facility aregenerally known as tonography and the C value is typically expressed interms of microliters per minute per millimeter of mercury. The C valueis determined by raising the intraocular pressure using the movablecentral piece of the contact device and observing the subsequent decayin intraocular pressure with respect to time. The elevated intraocularpressure increases the rate of aqueous outflow which, in turn, providesa change in volume. This change in volume can be calculated from theFriedenwald tables which correlate volume change to pressure changes.The rate of volume decrease equals the rate of outflow. The change inintraocular pressure during the tonographic procedure can be computed asan arithmetical average of pressure increments for successive 1/2 minuteintervals. The C value is derived then from the following equation:C=ΔV/t* (Pave-Po), in which t is the duration of the procedure, Pave isthe average pressure elevation during the test and can be measured, Pois the initial pressure and it is also measured, and ΔV is differencebetween the initial and final volumes and can be obtained from knowntables. The Flow ("F") of fluid is then calculated using the formula:F=C* (Po-Pv), in which Pv is the pressure in the episcleral veins whichcan be measured and generally has a constant value of 10.

2. Constant Depth Indentation

When constant depth indentation techniques are utilized, the methodinvolves the use of a variable force which is necessary to cause acertain predetermined amount of indentation in the eye. The apparatus ofthe present invention is therefore configured so as to measure the forcerequired to indent the cornea by a predetermined amount. This amount ofindentation may be detected using optical means as previously described.The movable central piece is pressed against the cornea to indent theeye, for example, by approximately 0.5 mm. The amount of indentation isdetected by the optical means and filters previously described. With thecentral piece indenting the cornea using a force equivalent to a weightof 10 grams, a 0.5 mm indentation will be achieved under normal pressureconditions (e.g., intraocular pressure of 15 mm Hg) and assuming thereis an average corneal curvature. With that amount of indentation andusing standard dimensions for the central piece, 2.5 mm³ of fluid willbe displaced. The force recorded by the present invention undergoes aslow decline and it levels off at a more or less steady state valueafter 2 to 4 minutes. The decay in pressure is measured based on thedifference between the value of the first indentation of the centralpiece and the final level achieved after a certain amount of time. Thepressure drop is due to the return of pressure to its normal value,after it has been artificially raised by the indentation caused by themovable central piece. A known normal value of decay is used as areference and is compared to the values obtained. Since the foregoingprovides a continuous recording of pressure over time, this method canbe an important tool for physiological research by showing, for example,an increase in pressure during forced expiration. The pulse wave andpulse amplitude can also be evaluated and the pulsatile blood flowcalculated.

3. Constant Pressure Indentation

When constant pressure indentation techniques are utilized, theintraocular pressure is kept constant by increasing the magnetic fieldand thereby increasing the force against the cornea as fluid leaks outof the eye. At any constant pressure, the force and rate of outflow arelinearly related according to the Friedenwald tonometry tables. Theintraocular pressure is calculated using the same method as describedfor conventional indentation tonometry. The volume displacement iscalculated using the tonometry tables. The facility of outflow (C) maybe computed using two different techniques. According to the firsttechnique, C can be calculated from two constant pressure tonograms atdifferent pressures according to the equation, C={[(ΔV₁ /t₁)-(ΔV₂/t₂)]/(P₁ -P₂)}, in which 1 corresponds to a measurement at a firstpressure and 2 corresponds to a measurement at a second pressure (whichis higher than the first pressure). The second way to calculate C isfrom one constant pressure tonogram and an independent measure ofintraocular pressure using applanation tonometry (P_(a)) inC=[(ΔV/t)/(P-P_(a) -ΔP_(e))], where ΔP_(e) is a correction factor forrise in episcleral venous pressure with indentation tonometry and P isthe intraocular pressure obtained using indentation tonometry.

4. Constant Pressure Applanation

When constant pressure applanation techniques are utilized, theintraocular pressure is kept constant by increasing the magnetic fieldand thus the force as fluid leaks out of the eye. If the cornea isconsidered to be a portion of a sphere, a mathematical formula relatesthe volume of a spherical segment to the radius of curvature of thesphere and the radius of the base of the segment. The volume displacedis calculated based on the formula V=A² /(4*π*R), in which V is volume,A is the area of the segment base, and R is the radius of curvature ofthe sphere (this is the radius of curvature of the cornea). SinceA=weight/pressure, then V=W² /(4*π*R*P²). The weight is constituted bythe force in the electromagnetic field, R is the curvature of the corneaand can be measured with a keratometer, P is the pressure in the eye andcan be measured using the same method as described for conventionalapplanation tonometry. It is therefore possible to calculate the volumedisplaced and the C value or outflow facility. The volume displaced, forexample, can be calculated at 15 second intervals and is plotted as afunction of time.

5. Constant Area Applanation

When constant area applanation techniques are utilized, the methodconsists primarily of evaluating the pressure decay curve while theflattened area remains constant. The aforementioned optical applanationdetecting arrangements can be used in order to keep constant the areaflattened by the movable central piece. The amount of force necessary tokeep the flattened area constant decreases and this decrease isregistered. The amount of volume displaced according to the differentareas of applanation is known. For instance, a 5 mm applanating centralpiece displaces 4.07 mm³ of volume for the average corneal radius of 7.8mm. Using the formula ΔV/Δt=1/(R*ΔP), it is possible to calculate Rwhich is the reciprocal of C. Since a continuous recording of pressureover time is provided, this method can be an important tool for researchand evaluation of blood flow.

6. Constant Force Applanation

When constant force applanation techniques are utilized, the same forceis constantly applied and the applanated area is measured using any ofthe aforementioned optical applanation detection arrangements. Once thearea flattened by a known force is measured, the pressure can becalculated by dividing the force by the amount of area that isapplanated. As fluid leaves the eye the amount of area applanatedincreases with time. This method consists primarily of evaluating aresulting area augmentation curve while the constant force is applied.The amount of volume displaced according to the different areas ofapplanation is known. Using the formula ΔV/Δt=1/(R*ΔP), it is possibleto calculate R which is the reciprocal of C.

Still additional uses of the present invention relate to detecting thefrequency response of the eye, using indentation tonometry. Inparticular, if an oscillating force is applied using the movable centralpiece 16, the velocity of the movable central piece 16 is indicative ofthe eye's frequency response. The system oscillates at the resonantfrequency determined primarily by the mass of the movable central piece16. By varying the frequency of the force and by measuring the response,the intraocular pressure can be evaluated. The evaluation can be made bymeasuring the resonant frequency and a significant variation in resonantfrequency can be obtained as a function of the intraocular pressure.

The present invention may also be used with the foregoing conventionalindentation techniques, but where the intraocular pressure used forcalculation is measured using applanation principles. Since applanationvirtually does not disturb the hydrodynamic equilibrium because itdisplaces a very small volume, this method can be considered moreaccurate than intraocular pressure measurements made using traditionalindentation techniques.

Another use of the present invention involves a time related way ofmeasuring the resistance to outflow. In particular, the resistance tooutflow is detected by measuring the amount of time necessary totransfigure the cornea with either applanation or indentation. The timenecessary to displace, for example, 5 microliters of eye fluid would be1 second for normal patients and above 2 seconds for glaucoma-strickenindividuals.

Yet another use of the present invention involves measuring the inflowof eye fluid. In particular, this measurement is made by applying theformula F=ΔP/R, in which ΔP is P-P_(v), and P is the steady stateintraocular pressure and P_(v) is the episcleral venous pressure which,for purposes of calculation, is considered constant at 10. R is theresistance to outflow, which is the reciprocal of C that can becalculated. F, in units of volume/min, can then be calculated.

The present invention is also useful at measuring ocular rigidity, orthe distensibility of the eye in response to an increased intraocularpressure. The coefficient of ocular rigidity can be calculated using anomogram which is based on two tonometric readings with differentweights. A series of conversion tables to calculate the coefficient ofocular rigidity was developed by Friedenwald. The technique fordetermining ocular rigidity is based on the concept of differentialtonometry, using two indentation tonometric readings with differentweights or more accurately, using one indentation reading and oneapplanation reading and plotting these readings on the nomogram. Sincethe present invention can be used to measure intraocular pressure usingboth applanation and indentation techniques, a more accurate evaluationof the ocular rigidity can be achieved.

Measurements of intraocular pressure using the apparatus of the presentinvention can also be used to evaluate hemodynamics, in particular, eyehemodynamics and pulsatile ocular blood flow. The pulsatile ocular bloodflow is the component of the total ocular arterial inflow that causes arhythmic fluctuation of the intraocular pressure. The intraocularpressure varies with each pulse due to the pulsatile influx of a bolusof arterial blood into the eye with each heartbeat. This bolus of bloodenters the intraocular arteries with each heartbeat causing a temporaryincrease in the intraocular pressure. The period of inflow causes astretching of the eye walls with a concomitant increase in pressurefollowed by a relaxation to the previous volume and a return to theprevious pressure as the blood drains from the eye. If this process ofexpansion during systole (contraction of the heart) and contractionduring diastole (relaxation of the heart) occurs at a certain pulserate, then the blood flow rate would be the incremental change in eyevolume times the pulse rate.

The fact that intraocular pressure varies with time according to thecardiac cycle is the basis for measuring pulsatile ocular blood flow.The cardiac cycle is approximately in the order of 0.8 Hz. The presentinvention can measure the time variations of intraocular pressure with afrequency that is above the fundamental human heart beat frequencyallowing the evaluation and recording of intraocular pulse. In thenormal human eye, the intraocular pulse has a magnitude of approximately3 mm Hg and is practically synchronous with the cardiac cycle.

As described, measurements of intraocular pressure show a time variationthat is associated with the pulsatile component of arterial pressure.Experimental results provide means of transforming ocular pressurechanges into eye volume changes. Each bolus of blood entering the eyeincreases the ocular volume and the intraocular pressure. The observedchanges in pressure reflect the fact that the eye volume must change toaccommodate changes in the intraocular blood volume induced by thearterial blood pulse. This pulse volume is small relative to the ocularvolume, but because the walls of the eye are stiff, the pressureincrease required to accommodate the pulse volume is significant and canbe measured. Therefore, provided that the relationship between theincreased intraocular pressure and increased ocular volume is known, thevolume of the bolus of fluid can be determined. Since this relationshipbetween pressure change and volume change has been well established(Friedenwald 1937, McBain 1957, Ytteborg 1960, Eisenlohr 1962, McEwen1965), the pressure measurements can be used to obtain the volume of abolus of blood and thereby determine the blood flow.

The output of the tonometer for the instantaneous pressure can beconverted into instantaneous change in eye volume as a function of time.The time derivative of the change in ocular volume is the netinstantaneous pulsatile component of the ocular blood flow. Under theseconditions, the rate of pulsatile blood flow through the eye can be.evaluated from the instantaneous measurement of intraocular pressure. Inorder to rapidly quantify and analyze the intraocular pulse, the signalfrom the tonometer may be digitalized and fed into a computer.

Moreover, measurements of intraocular pressure can be used to obtain theintraocular volume through the use of an independently determinedpressure-volume relationship such as with the Friedenwald equation(Friedenwald, 1937). A mathematical model based on experimental datafrom the pressure volume relationship (Friedenwald 1937, McBain 1957,Eisenlohr 1962, McEwen 1965) can also be used to convert a change inocular pressure into a change in ocular volume.

In addition, a model can also be constructed to estimate the ocularblood flow from the appearance of the intraocular pressure waveform. Theflow curve is related to parameters that come from the volume changecurve. This curve is indirectly measured since the intraocular pressureis the actual measured quantity which is transformed into volume changethrough the use of the measured pressure-volume relation. The flow isthen computed by taking the change in volume Vmax-Vmin multiplied by aconstant that is related to the length of the time interval of theinflow and the total pulse length. Known mathematical calculations canbe used to evaluate the pulsatile component of the ocular blood flow.Since the present invention can also be used to measure the ocularrigidity, this parameter of coefficient of ocular rigidity can be usedin order to more precisely calculate individual differences in pulsatileblood flow.

Moreover, since the actuation apparatus 6 and contact device 2 of thepresent invention preferably include transparent portions, the pulsatileblood flow can be directly evaluated optically to quantify the change insize of the vessels with each heart beat. A more precise evaluation ofblood flow therefore can be achieved by combining the changes inintraocular pulse with changes in vessel diameter which can beautomatically measured optically.

A vast amount of data about the vascular system of the eye and centralnervous system can be obtained after knowing the changes in intraocularpressure over time and the amount of pulsatile ocular blood flow. Theintraocular pressure and intraocular pulse are normally symmetrical inpairs of eyes. Consequently, a loss of symmetry may serve as an earlysign of ocular or cerebrovascular disease. Patients afflicted withdiabetes, macular degeneration, and other vascular disorders may alsohave a decreased ocular blood flow and benefit from evaluation of eyehemodynamics using the apparatus of the present invention.

The present invention may also be used to artificially elevateintraocular pressure. The artificial elevation of intraocular pressureis an important tool in the diagnosis and prognosis of eye and braindisorders as well as an important tool for research.

Artificial elevation of intraocular pressure using the present inventioncan be accomplished in different ways. According to one way, the contactdevice of the present invention is modified in shape for placement onthe sclera (white of the eye). This arrangement, which will be describedhereinafter, is illustrated in FIGS. 21-22, wherein the movable centralpiece 16 may be larger in size and is preferably actuated against thesclera in order to elevate the intraocular pressure. The amount ofindentation can be detected by the optical detection system previouslydescribed.

Another way of artificially increasing the intraocular pressure is byplacing the contact device of the present invention on the cornea in thesame way as previously described, but using the movable central piece toapply a greater amount of force to achieve deeper indentation. Thistechnique advantageously allows visualization of the eye while exertingthe force, since the movable central portion of the contact device ispreferably transparent. According to this technique, the size of themovable central piece can also be increased to indent a larger area andthus create a higher artificial increase of intraocular pressure.Preferably, the actuation apparatus also has a transparent centralportion, as indicated above, to facilitate direct visualization of theeye and retina while the intraocular pressure is being increased. Whenthe intraocular pressure exceeds the ophthalmic arterial diastolicpressure, the pulse amplitude and blood flow decreases rapidly. Bloodflow becomes zero when the intraocular pressure is equal or higher thanthe ophthalmic systolic pressure. Thus, by allowing direct visualizationof the retinal vessels, one is able to determine the exact moment thatthe pulse disappears and measure the pressure necessary to promote thecessation of the pulse which, in turn, is the equivalent of the pulsepressure in the ophthalmic artery. The present invention thus allows themeasurement of the pressure in the arteries of the eye.

Also, by placing a fixation light in a back portion of the actuationapparatus and asking the patient to indicate when he/she can no longersee the light, one can also record the pressure at which a patient'svision ceases. This also would correspond to the cessation of the pulsein the artery of the eye. The pressure in which vessels open can also bedetermined by increasing intraocular pressure until the pulse disappearsand then gradually decreasing the intraocular pressure until the pulsereappears. Thus, the intraocular pressure necessary for vessels to opencan be evaluated.

It is important to note that the foregoing measurements can be performedautomatically using an optical detection system, for example, by aiminga light beam at the pulsating blood vessel. The cessation of pulsationcan be optically recognized and the pressure recorded. An attenuation ofpulsations can also be used as the end point and can be opticallydetected. The apparatus also allows direct visualization of the papillaof the optic nerve while an increased intraocular pressure is produced.Thus, physical and chemical changes occurring inside the eye due to theartificial increase in intraocular pressure may be evaluated at the sametime that pressure is measured.

Advantageously, the foregoing, test can be performed on patients withmedia opacities that prevent visualization of the back of the eye. Inparticular, the aforementioned procedure wherein the patient indicateswhen vision ceases is particular useful in patients with mediaopacities. The fading of the peripheral vision corresponds to thediastolic pressure and fading of the central vision corresponds to thesystolic pressure.

The present invention, by elevating the intraocular pressure, asindicated above and by allowing direct visualization of blood vessels inthe back of the eye, may be used for tamponade (blockade of bleeding byindirect application of pressure) of hemorrhagic processes such as thosewhich occur, for example, in diabetes and macular degeneration. Theelevation of intraocular pressure may also be beneficial in thetreatment of retinal detachments.

As yet another use of the present invention, the aforementionedapparatus also can be used to measure outflow pressure of the eye fluid.In order to measure outflow pressure in the eye fluid, the contactdevice is placed on the cornea and a measurable pressure is applied tothe cornea. The pressure causes the aqueous vein to increase in diameterwhen the pressure in the cornea equals the outflow pressure. Thepressure on the cornea is proportional to the outflow pressure. The flowof eye fluid out of the eye is regulated according to Poiseuille's Lawfor laminar currents. If resistance is inserted into the formula, theresult is a formula similar to Ohm's Law. Using these known formulas,the rate of flow (volume per time) can be determined. The change in thediameter of the vessel which is the reference point can be detectedmanually by direct observation and visualization of the change indiameter or can be done automatically using an optical detection systemcapable of detecting a change in reflectivity due to the amount of fluidin the vein and the change in the surface area. The actual cross-sectionof the vein can be detected using an optical detection system.

The eye and the brain are hemodynamically linked by the carotid arteryand the autonomic nervous system. Pathological changes in the carotid,brain, heart, and the sympathetic nervous system can secondarily affectthe blood flow to the eye. The eye and the brain are low vascularresistance systems with high reactivity. The arterial flow to the brainis provided by the carotid artery. The ophthalmic artery branches off ofthe carotid at a 90 degree angle and measures approximately 0.5 mm indiameter in comparison to the carotid which measures 5 mm in diameter.Thus, most processes that affect the flow to the brain will have aprofound effect on the eye. Moreover, the pulsation of the centralretinal artery may be used to determine the systolic pressure in theophthalmic artery, and due to its anatomic relationship with thecerebral circulatory system, the pressure in the brain's vessels can beestimated. Total or partial occlusion of the vascular system to thebrain can be determined by evaluating the ocular blood flow. There arenumerous vascular and nervous system lesions that alter the ocular pulseamplitude and/or the intraocular pressure curve of the eye. Thesepathological situations may produce asymmetry of measurements betweenthe two eyes and/or a decrease of the central retinal artery pressure,decrease of pulsatile blood flow and alter the pulse amplitude.

An obstruction in the flow in the carotid (cerebral circulation) can beevaluated by analyzing the ocular pulse amplitude and area, pulse delayand pulse width, form of the wave and by harmonic analysis of the ocularpulse.

The eye pulsation can be recorded optically according to the change inreflection of the light beam projected to the cornea. The same systemused to record distance traveled by the movable central piece duringindentation can be used on the bare cornea to detect the changes involume that occurs with each pulsation. The optical detection systemrecords the variations in distance from the surface of the cornea thatoccurs with each heart beat. These changes in the position of the corneaare induced by the volume changes in the eye. From the pulsatilecharacter of these changes, the blood flow to the eye can be calculated.

With the aforementioned technique of artificial elevation of pressure,it is possible to measure the time necessary for the eye to recover toits baseline and this recovery time is an indicator of the presence ofglaucoma and of the coefficient of outflow facility.

The present invention may also be used to measure pressure in thevessels on the surface of the eye, in particular the pressure in theepiscleral veins. The external pressure necessary to collapse a vein isutilized in this measurement. The method involves applying a variableforce over a constant area of conjunctive overlying the episcleral veinuntil a desired end point is obtained. The pressure is applied directlyonto the vessel itself and the preferred end point is when the vesselcollapses. However, different end points may be used, such as blanchingof the vessel which occurs prior to the collapse. The pressure of theend point is determined by dividing the force applied by the area of theapplanating central piece in a similar way as is used for tonometry. Thevessel may be observed through a transparent applanating movable centralpiece using a slit-lamp biomicroscope. The embodiment for this techniquepreferably includes a modified contact device which fits on the sclera(FIG. 23). The preferred size of the tip ranges from 250 micrometers to500 micrometers. Detection of the end point can be achieved eithermanually or automatically.

According to the manual arrangement, the actuation apparatus isconfigured for direct visualization of the vessel through a transparentback window of the actuation apparatus, and the time of collapse ismanually controlled and recorded. According to an automatic arrangement,an optical detection system is configured so that, when the blood streamis no longer visible, there is a change in a reflected light beam in thesame way as described above for tonometry, and consequently, thepressure for collapse is identifiable automatically. The end pointmarking in both situations is the disappearance of the blood stream, onedetected by the operator's vision and the other detected by an opticaldetection system. Preferably, in both cases, the contact device isdesigned in a way to fit the average curvature of the sclera and themovable central piece, which can be a rigid or flexible material, isused to compress the vessel.

The present invention may also be used to provide real-time recording ofintraocular pressure. A built-in single chip microprocessor can be maderesponsive to the intraocular pressure measurements over time and can beprogrammed to create and display a curve relating pressure to time. Therelative position of the movable central piece can be detected, asindicated above, using an optical detection system and the detectedposition in combination with information regarding the amount of currentflowing through the coil of the actuation apparatus can be rapidlycollected and analyzed by the microprocessor to create theaforementioned curve.

It is understood that the use of a microprocessor is not limited to thearrangement wherein curves are created. In fact, microprocessortechnology may be used to create at least the aforementioned calculationunit 10 of the present invention. A microprocessor preferably evaluatesthe signals and the force that is applied. The resulting measurementscan be recorded or stored electronically in a number of ways. Thechanges in current over time, for example, can be recorded on astrip-chart recorder. Other methods of recording and storing the datacan be employed. Logic microprocessor control technology can also beused in order to better evaluate the data.

Still other uses of the present invention relate to evaluation ofpressure in deformable materials in industry and medicine. One suchexample is the use of the present invention to evaluate soft tissue,such as organs removed from cadavers. Cadaver dissection is afundamental method of learning and studying the human body. Thedeformability of tissues such as the brain, liver, spleen, and the like,can be measured using the present invention and the depth of indentationcan be evaluated. In this regard, the contact device of the presentinvention can be modified to fit over the curvature of an organ. Whenthe movable central piece rests upon a surface, it can be actuated toproject into the surface a distance which is inversely proportional tothe tension of the surface and rigidity of the surface to deformation.The present invention can also be used to evaluate and quantify theamount of cicatrization, especially in burn scar therapy. The presentinvention can be used to evaluate the firmness of the scar in comparisonto normal skin areas. The scar skin tension is compared to the value ofnormal skin tension. This technique can be used to monitor the therapyof patients with burn scars allowing a numerical quantification of thecourse of cicatrization. This technique can also be used as an earlyindicator for the development of hypertrophic (thick and elevated)scarring. The evaluation of the tissue pressure and deformability in avariety of conditions such as: a) lymphoedema b) post-surgical effects,such as with breast surgery, and c) endoluminal pressures of holloworgans, is also possible with the apparatus. In the above cases, thepiston-like arrangement provided by the contact device does not have tobe placed in an element that is shaped like a contact lens. To thecontrary, any shape and size can be used, with the bottom surfacepreferably being flat and not curved like a contact lens.

Yet another use of the present invention relates to providing a bandagelens which can be used for extended periods of time. Glaucoma andincreased intraocular pressure are leading causes for rejection ofcorneal transplants. Many conventional tonometers in the market areunable to accurately measure intraocular pressure in patients withcorneal disease. For patients with corneal disease and who have recentlyundergone corneal transplant, a thinner and larger contact device isutilized and this contact device can be used for a longer period oftime. The device also facilitates measurement of intraocular pressure inpatients with corneal disease which require wearing of contact lenses aspart of their treatment.

The present invention may also be modified to non-invasively measureinfant intracranial pressure, or to provide instantaneous and continuousmonitoring of blood pressure through an intact wall of a blood vessel.The present invention may also be used in conjunction with a digitalpulse meter to provide synchronization with the cardiac cycle. Also, byproviding a contact microphone, arterial pressure can be measured. Thepresent invention may also be used to create a dual tonometerarrangement in one eye. A first tonometer can be defined by the contactdevice of the present invention applied over the cornea, as describedabove. The second tonometer can be defined by the previously mentionedcontact device which is modified for placement on the temporal sclera.In using the dual tonometer arrangement, it is desirable to permitlooking into the eye at the fundus while the contact devices are beingactuated. Accordingly, at least the movable central piece of the contactdevice placed over the cornea is preferably transparent so that thefundus can be observed with a microscope.

Although the foregoing illustrated embodiments of the contact devicegenerally show only one movable central piece 16 in each contact device2, it is understood that more than one movable central piece 16 can beprovided without departing from the scope and spirit of the presentinvention. Preferably, the multiple movable central pieces 16 would beconcentrically arranged in the contact device 2, with at least one ofthe flexible membranes 14 interconnecting the concentrically arrangedmovable central pieces 16. This arrangement of multiple movable centralpieces 16 can be combined with any of the aforementioned features toachieve a desired overall combination.

Although the foregoing preferred embodiments include at least onemagnetically actuated movable central piece 16, it is understood thatthere are many other techniques for actuating the movable central piece16. Sound or ultrasound generation techniques, for example, can be usedto actuate the movable central piece. In particular, the sonic orultrasonic energy can be directed to a completely transparent version ofthe movable central piece which, in turn, moves in toward the cornea inresponse to the application of such energy.

Similarly, the movable central piece may be provided with means forretaining a static electrical charge. In order to actuate such a movablecentral piece, an actuation mechanism associated therewith would createan electric field of like polarity, thereby causing repulsion of themovable central piece away from the source of the electric field.

Other actuation techniques, for example, include the discharge of fluidor gas toward the movable central piece, and according to a lessdesirable arrangement, physically connecting the movable central pieceto a mechanical actuation device which, for example, may be motor drivenand may utilize a strain gauge.

Alternatively, the contact device may be eliminated in favor of amovable central piece in an actuation apparatus. According to thisarrangement, the movable central piece of the actuation apparatus may beconnected to a slidable shaft in the actuation apparatus, which shaft isactuated by a magnetic field or other actuation means. Preferably, aphysician applies the movable central piece of the actuation apparatusto the eye and presses a button which generates the magnetic field.This, in turn, actuates the shaft and the movable central piece againstthe eye. Preferably, the actuation apparatus, the shaft, and the movablecentral piece of the actuation apparatus are appropriately arranged withtransparent portions so that the inside of the patient's eye remainsvisible during actuation.

Any of the above described detection techniques, including the opticaldetection technique, can be used with the alternative actuationtechniques.

Also, the movable central piece 16 may be replaced by an inflatablebladder (not shown) disposed of the substantially rigid annular member12. When inflated, the bladder extends out of the hole in thesubstantially rigid annular member 12 and toward the cornea.

Similarly, although some of the foregoing preferred embodiments utilizean optical arrangement for determining when the predetermined amount ofapplanation has been achieved, it is understood that there are manyother techniques for determining when applanation occurs. The contactdevice, for example, may include an electrical contact arranged so as tomake or break an electrical circuit when the movable central piece movesa distance corresponding to that which is necessary to produceapplanation. The making or breaking of the electrical circuit is thenused to signify the occurrence of applanation.

It is also understood that, after applanation has occurred, the timewhich it takes for the movable central piece 16 to return to thestarting position after termination of the actuating force will beindicative of the intraocular pressure, when the intraocular pressure ishigh, the movable central piece 16 returns more quickly to the startingposition. Similarly, for lower intraocular pressures, it takes longerfor the movable central piece 16 to return to its starting position.Therefore, the present invention can be configured to also consider thereturn time of the movable central piece 16 in determining the measuredintraocular pressure.

As indicated above, the present invention may be formed with atransparent central portion in the contact device. This transparentcentral portion advantageously permits visualization of the inside ofthe eye (for example, the optic nerve) while the intraocular pressure isartificially increased using the movable central piece. Some of theeffects of increased intraocular pressure on the optic nerve, retina,and vitreous are therefore readily observable through the presentinvention, while intraocular pressure is measured simultaneously.

With reference to FIGS. 21 and 22, although the foregoing examplesdescribe placement of the contact device 2 on the cornea, it isunderstood that the contact device 2 of the present invention may beconfigured with a quasi-triangular shape (defined by the substantiallyrigid annular member) to facilitate placement of the contact device 2 onthe sclera of the eye.

With reference to FIGS. 23 and 24, the contact device 2 of the presentinvention may be used to measure episcleral venous pressure. Preferably,when episcleral venous pressure is to be measured, the movable centralpiece 6 has a transparent centrally disposed frustoconical projection16P. The embodiment illustrated FIG. 24 advantageously permitsvisualization of the subject in through at least the transparent centralportion of the movable central piece 16.

Furthermore, as indicated above, the present invention may also be usedto measure pressure in other parts of the body (for example, scarpressure in the context of plastic surgery) or on surfaces of variousobjects. The contact device of the present invention, therefore, is notlimited to the corneal-conforming curved shape illustrated in connectionwith the exemplary embodiments, but rather may have various other shapesincluding a generally flat configuration.

ALTERNATIVE EMBODIMENT ACTUATED BY CLOSURE OF THE EYE LID

With reference to FIGS. 25-31, an alternative embodiment of the systemwill now be described. The alternative apparatus and method uses theforce and motion generated by the eye lid during blinking and/or closureof the eyes to act as the actuation apparatus and activate at least onetransducer 400 mounted in the contact device 402 when the contact device402 is on the cornea. The method and device facilitate the remotemonitoring of pressure and other physiological events by transmittingthe information through the eye lid tissue, preferably viaelectromagnetic waves. The information transmitted is recovered at areceiver 404 remotely placed with respect to the contact device 402,which receiver 404 is preferably mounted in the frame 408 of a pair ofeye glasses. This alternative embodiment also facilitates utilization offorceful eye lid closure to measure outflow facility. The transducer ispreferably a microminiature pressure-sensitive transducer 400 thatalters a radio frequency signal in a manner indicative of physicalpressure exerted on the transducer 400.

Although the signal response from the transducer 400 can be communicatedby cable, it is preferably actively or passively transmitted in awireless manner to the receiver 404 which is remotely located withrespect to the contact device 402. The data represented by the signalresponse of the transducer 400 can then be stored and analyzed.Information derived from this data can also be communicated by telephoneusing conventional means.

According to the alternative embodiment, the apparatus comprises atleast one pressure-sensitive transducer 400 which is preferablyactivated by eye lid closure and is mounted in the contact device 402.The contact device 402, in turn, is located on the eye. In order tocalibrate the system, the amount of motion and squeezing of the contactdevice 402 during eye lid motion/closure is evaluated and calculated. Asthe upper eyelid descends during blinking, it pushes down and squeezesthe contact device 402, thereby forcing the contact device 402 toundergo a combined sliding and squeezing motion.

Since normal individuals involuntarily blink approximately every 2 to 10seconds, this alternative embodiment of the present invention providesfrequent actuation of the transducer 400. In fact, normal individualswearing a contact device 402 of this type will experience an increase inthe number of involuntary blinks, and this, in turn, tends to providequasi-continuous measurements. During sleep or with eyes closed, sincethere is uninterrupted pressure by the eye lid, the measurements can betaken continuously.

As indicated above, during closure of the eye, the contact device 402undergoes a combined squeezing and sliding motion caused by the eye lidduring its closing phase. Initially the upper eye lid descends from theopen position until it meets the upper edge of the contact device 402,which is then pushed downward by approximately 0.5 mm to 2 mm. Thisdistance depends on the type of material used to make the structure 412of the contact device 402 and also depends on the diameter thereof.

When a rigid structure 412 is used, there is little initial overlapbetween the lid and the contact device 402. When a soft structure 412 isused, there is a significant overlap even during this initial phase ofeye lid motion. After making this initial small excursion the contactdevice 402 comes to rest, and the eye lid then slides over the outersurface of the contact device 402 squeezing and covering it. It isimportant to note that if the diameter of the structure 412 is greaterthan the lid aperture or greater than the corneal diameter, the upperlid may not strike the upper edge of the contact device 402 at thebeginning of a blink.

The movement of the contact device 402 terminates approximately at thecorneo-scleral junction due to a slope change of about 13 degrees in thearea of intersection between cornea (radius of 9 mm) and sclera (radiusof 11.5 mm). At this point the contact device 402, either with a rigidor soft structure 412, remains immobile and steady while the eye lidproceeds to cover it entirely.

When a rigid structure 412 is used, the contact device 402 is usuallypushed down 0.5 mm to 2 mm before it comes to rest. When a softstructure 412 is used, the contact device 402 is typically pushed down0.5 mm or less before it comes to rest. The larger the diameter of thecontact device 402, the smaller the motion, and when the diameter islarge enough there may be zero vertical motion. Despite thesedifferences in motion, the squeezing effect is always present, therebyallowing accurate measurements to be taken regardless of the size of thestructure 412. Use of a thicker structure 412 or one with a flattersurface results in an increased squeezing force on the contact device402.

The eye lid margin makes a re-entrant angle of about 35 degrees withrespect to the cornea. A combination of forces, possibly caused by thecontraction of the muscle of Riolan near the rim of the eye lid and ofthe orbicularis muscle, are applied to the contact device 402 by the eyelid. A horizontal force (normal force component) of approximately 20,000to 25,000 dynes and a vertical force (tangential force component) ofabout 40 to 50 dynes is applied on the contact device 402 by the uppereye lid. In response to these forces, the contact device 402 moves bothtoward the eye and tangentially with respect thereto. At the moment ofmaximum closure of the eye, the tangential motion and force are zero andthe normal force and motion are at a maximum.

The horizontal lid force of 20,000 to 25,000 dynes pressing the contactdevice 402 against the eye generates enough motion to activate thetransducer 400 mounted in the contact device 402 and to permitmeasurements to be performed. This eye lid force and motion toward thesurface of the eye are also capable of sufficiently deforming many typesof transducers or electrodes which can be mounted in the contact device402. During blinking, the eye lids are in full contact with the contactdevice 402 and the surface of each transducer 400 is in contact with thecornea/tear film and/or inner surface of the eye lid.

The microminiature pressure-sensitive radio frequency transducer 400preferably consists of an endoradiosonde mounted in the contact device402 which, in turn, is preferably placed on the cornea and is activatedby eye lid motion and/or closure. The force exerted by the eye lid onthe contact device 402, as indicated above, presses it against thecornea.

According to a preferred alternative embodiment illustrated in FIG. 26,the endoradiosonde includes two opposed matched coils which are placedwithin a small pellet. The flat walls of the pellet act as diaphragmsand are attached one to each coil such that compression of the diaphragmby the eye lid brings the coils closer to one another. Since the coilsare very close to each other, minimal changes in their separation affecttheir resonant frequency.

A remote grid-dip oscillator 414 may be mounted at any convenientlocation near the contact device 402, for example, on a hat or cap wornby the patient. The remote grid-dip oscillator 414 is used to induceoscillations in the transducer 400. The resonant frequency of theseoscillations is indicative of intraocular pressure.

Briefly, the contact of the eye lid with the diaphragms forces a pair ofparallel coaxial archimedean-spiral coils in the transducer 400 to movecloser together. The coils constitute a high-capacitance distributedresonant circuit having a resonant frequency that varies according torelative coil spacing. When the coils approach one another, there is anincrease in the capacitance and mutual inductance, thereby lowering theresonant frequency of the configuration. By repeatedly scanning thefrequency of an external inductively coupled oscillating detector of thegrid-dip type, the electromagnetic energy which is absorbed by thetransducer 400 at its resonance is sensed through the intervening eyelid tissue.

Pressure information from the transducer 400 is preferably transmittedby radio link telemetry. Telemetry is a preferred method since it canreduce electrical noise pickup and eliminates electric shock hazards. FM(frequency modulation) methods of transmission are preferred since FMtransmission is less noisy and requires less gain in the modulationamplifier, thus requiring less power for a given transmission strength.FM is also less sensitive to variations in amplitude of the transmittedsignal.

Several other means and transducers can be used to acquire a signalindicative of intraocular pressure from the contact device 402. Forexample, active telemetry using transducers which are energized bybatteries or using cells that can be recharged in the eye by an externaloscillator, and active transmitters which can be powered from a biologicsource can also be used.

The preferred method to acquire the signal, however, involves at leastone of the aforementioned passive pressure sensitive transducers 400which contain no internal power source and operate using energy suppliedfrom an external source to modify the frequency emitted by the externalsource. Signals indicative of intraocular ocular pressure are based onthe frequency modification and are transmitted to remote extra-ocularradio frequency monitors. The resonant frequency of the circuit can beremotely sensed, for example, by a grid-dip meter.

In particular, the grip-dip meter includes the aforementioned receiver404 in which the resonant frequency of the transducer 400 can bemeasured after being detected by external induction coils 415 mountednear the eye, for example, in the eyeglass frames near the receiver orin the portion of the eyeglass frames which surround the eye. The use ofeyeglass frames is especially practical in that the distance between theexternal induction coils 415 and the radiosonde is within the typicalworking limits thereof. It is understood, however, that the externalinduction coils 415, which essentially serve as a receiving antenna forthe receiver 404 can be located any place that minimizes signalattenuation. The signal from the external induction coils 415 (orreceiving antenna) is then received by the receiver 404 foramplification and analysis.

When under water, the signal may be transmitted using modulated soundsignals because sound is less attenuated by water than are radio waves.The sonic resonators can be made responsive to changes in temperatureand voltage.

Although the foregoing description includes some preferred methods anddevices in accordance with the alternative embodiment of the presentinvention, it is understood that the invention is not limited to thesepreferred devices and methods. For example, many other types ofminiature pressure sensitive radio transmitters can be used and mountedin the contact device, and any microminiature pressure sensor thatmodulates a signal from a radio transmitter and sends the modulatedsignal to a nearby radio receiver can be used.

Other devices such as strain gauges, preferably piezoelectric pressuretransducers, can also be used on the cornea and are preferably activatedby eye lid closure and blinking. Any displacement transducer containedin a distensible case also can be mounted in the contact device. Infact, many types of pressure transducers can be mounted in and used bythe contact device. Naturally, virtually any transducer that cantranslate the mechanical deformation into electric signals is usable.

Since the eye changes its temperature in response to changes inpressure, a pressure-sensitive transducer which does not require motionof the parts can also be used, such as a thermistor. Alternatively, thedielectric constant of the eye, which also changes in response topressure changes, can be evaluated to determine intraocular pressure. Inthis case, a pressure-sensitive capacitor can be used. Piezoelectric andpiezo-resistive transducers, silicon strain gauges, semiconductordevices and the like can also be mounted and activated by blinkingand/or closure of the eyes.

In addition to providing a novel method for performing singlemeasurements, continuous measurements, and self-measurement ofintraocular pressure during blinking or with the eyes closed, theapparatus can also be used to measure outflow facility and otherphysiological parameters. The inventive method and device offer a uniqueapproach to measuring outflow facility in a physiological manner andundisturbed by the placement of an external weight on the eye.

In order to determine outflow facility in this fashion, it is necessaryfor the eye lid to create the excess force necessary to squeeze fluidout of the eye. Because the present invention permits measurement ofpressure with the patient's eyes closed, the eye lids can remain closedthroughout the procedure and measurements can be taken concomitantly. Inparticular, this is accomplished by forcefully squeezing the eye lidsshut. Pressures of about 60 mm Hg will occur, which is enough to squeezefluid out of the eye and thus evaluate outflow facility. The intraocularpressure will decrease over time and the decay in pressure with respectto time correlates to the outflow facility. In normal individuals, theintraocular fluid is forced out of the eye with the forceful closure ofthe eye lid and the pressure will decrease accordingly; however, inpatients with glaucoma, the outflow is compromised and the eye pressuretherefore does not decrease at the same rate in response to the forcefulclosure of the eye lids. The present system allows real time andcontinuous measurement of eye pressure and, since the signal can betransmitted through the eye lid to an external receiver, the eyes canremain closed throughout the procedure.

Telemetry systems for measuring pressure, electrical changes,dimensions, acceleration, flow, temperature, bioelectric activity,chemical reactions, and other important physiological parameters andpower switches to externally control the system can be used in theapparatus of the invention. The use of integrated circuits and technicaladvances occurring in transducer, power source, and signal processingtechnology allow for extreme miniaturization of the components which, inturn, permits several sensors to be mounted in one contact device, asillustrated for example in FIG. 28.

Modern resolutions of integrated circuits are in the order of a fewmicrons and facilitate the creation of very high density circuitarrangements. Preferably, the modern techniques of manufacturingintegrated circuits are exploited in order to make electronic componentssmall enough for placement on the eyeglass frame 408. The receiver 404,for example, may be connected to various miniature electronic components418, 419, 420, as schematically illustrated in FIG. 31, capable ofprocessing, storing, and even displaying the information derived fromthe transducer 400.

Radio frequency and ultrasonic micro-circuits are available and can bemounted in the contact device for use thereby. A number of differentultrasonic and pressure transducers are also available and can be usedand mounted in the contact device. It is understood that furthertechnological advances will occur which will permit further applicationsof the apparatus of the invention.

The system may further comprise a contact device for placement on thecornea and having a transducer capable of detecting chemical changes inthe tear film. The system may further include a contact device forplacement on the cornea and having a microminiature gas-sensitive radiofrequency transducer (e.g., oxygen-sensitive). A contact device having amicrominiature blood velocity-sensitive radio frequency transducer mayalso be used for mounting on the conjunctiva and is preferably activatedby eye lid motion and/or closure of the eye lid.

The system also may comprise a contact device in which a radio frequencytransducer capable or measuring the negative resistance of nerve fibersis mounted in the contact device which, in turn, is placed on the corneaand is preferably activated by eye lid motion and/or closure of the eyelid. By measuring the electrical resistance, the effects ofmicroorganisms, drugs, poisons and anesthetics can be evaluated.

The system of the present invention may also include a contact device inwhich a microminiature radiation-sensitive radio frequency transducer ismounted in the contact device which, in turn, is placed on the corneaand is preferably activated by eye lid motion and/or closure of the eyelid.

In any of the foregoing embodiments having a transducer mounted in thecontact device, a grid-dip meter can be used to measure the frequencycharacteristics of the tuned circuit defined by the transducer.

Besides using passive telemetry techniques as illustrated by the use ofthe above transducers, active telemetry with active transmitters and amicrominiature battery mounted in the contact device can also be used.

The contact device preferably includes a rigid or flexible transparentstructure 412 in which at least one of the transducers 400 is mounted inhole(s) formed in the transparent structure 412. Preferably, thetransducers 400 is/are positioned so as to allow the passage of lightthrough the visual axis. The structure 412 preferably includes an innerconcave surface shaped to match an outer surface of the cornea.

As illustrated in FIG. 29, a larger transducer 400 can be centrallyarranged in the contact device 402, with a transparent portion 416therein preserving the visual axis of the contact device 402.

The structure 412 preferably has a maximum thickness at the center and aprogressively decreasing thickness toward a periphery of the structure412. The transducers is/are preferably secured to the structure 412 sothat the anterior side of each transducer 400 is in contact with theinner surface of the eye lid during blinking and so that the posteriorside of each transducer 400 is in contact with the cornea, thus allowingeye lid motion to squeeze the contact device 402 and its associatedtransducers 400 against the cornea.

Preferably, each transducer 400 is fixed to the structure 412 in such away that only the diaphragms of the transducers experience motion inresponse to pressure changes. The transducers 400 may also have anysuitable thickness, including matching or going beyond the surface ofthe structure 412.

The transducers 400 may also be positioned so as to bear against onlythe cornea or alternatively only against the inner surface of the eyelid. The transducers 400 may also be positioned in a protruding waytoward the cornea in such a way that the posterior part flattens aportion of the cornea upon eye lid closure. Similarly, the transducers400 may also be positioned in a protruding way toward the inner surfaceof the eye lid so that the anterior part of the transducer 400 ispressed by the eye lid, with the posterior part being covered by aflexible membrane allowing interaction with the cornea upon eye lidclosure.

A flexible membrane of the type used in flexible or hydrogel lenses mayencase the contact device 402 for comfort as long as it does notinterfere with signal acquisition and transmission. Although thetransducers 400 can be positioned in a manner to counterbalance eachother, as illustrated in FIG. 28, it is understood that a counter weightcan be used to maintain proper balance.

FIG. 32 illustrates the contact device 500 placed on the surface of theeye with mounted sensor 502, transmitter 504, and power source 506 whichare connected by fine wire 508 (shown only partially extending fromsensor 502 and from transmitter 504), encased in the contact device. Thecontact device shown measures approximately 24 mm in its largestdiameter with its corneal portion 510 measuring approximately 11 mm indiameter with the remaining 13 mm subdivided between 8 mm of a portion512 under the upper eyelid 513 and 5 mm of a portion 514 under the lowereyelid 515. The contact device in FIG. 32 has microprotuberances 516 inits surface which increases friction and adhesion to the conjunctivaallowing diffusion of tissue fluid from the blood vessels into thesensor selective membrane surface 518. The tissue fluid goes throughmembranes in the sensor and reaches an electrode 520 with generation ofcurrent proportional to the amount of analyte found in the tear fluid522 moving in the direction of arrows 524. A transmitter 504transmitting a modulated signal 526 to a receiver 528 with the signal526 being amplified and filtered in amplifier and filter 529, decoded indemultiplexer 530, processed in CPU 532, displayed at monitor 534, andstored in memory 536.

The contact device 540 shown in FIG. 33A includes two sensors, onesensor 542 for detection of glucose located in the main body 544 of thecontact device and a cholesterol sensor 546 located on a myoflange 548of the contact device 540. Forming part of the contact device is aheating electrode 550 and a power source 552 next to the cholesterolsensor 546 with the heating electrode 550 increasing the localtemperature with subsequent transudation of fluid in the direction ofarrows 553 toward the cholesterol sensor 546.

In one embodiment the cholesterol sensor shown in FIG. 33C includes anouter selectively permeable membrane 554, and mid-membranes 556, 558with immobilized cholesterol esterase and cholesterol oxidase enzymesand an inner membrane 560 permeable to hydrogen peroxide. The externalmembrane 554 surface has an area preferably no greater than 300 squaremicrometers and an overall thickness of the multiple membrane layers isin the order of 30-40 micrometers. Covered by the inner membrane are aplatinum electrode 562 and two silver electrodes 564 measuring 0.4 mm(platinum wire) and 0.15 mm (silver wire). Fine wires 566, 568 connectthe cholesterol sensor 546 to the power source 552 and transmitter 570.The glucose sensor 542 includes a surrounding irregular external surface572 to increase friction with the sensor connected by fine wires 574,576 to the power source 578 and transmitter 570. The power source 578 isconnected to the sensor in order to power the sensor 542 for operation.

The transmitter includes integrated circuits for receiving andtransmitting the data with the transmitters being of ultra denseintegrated hybrid circuits measuring approximately 500 microns in itslargest dimension. The corneal tissue fluid diffuses in the direction ofarrows 580 toward the glucose sensor 542 and reaches an outer membrane582 permeable to glucose and oxygen followed by an immobilized glucoseoxidase membrane 584 and an inner membrane 586 permeable to hydrogenperoxide. The tissue fluid then reaches the one platinum 588 and twosilver 590 electrodes generating a current proportional to theconcentration of glucose. The dimensions of the glucose sensor aresimilar to the dimensions of the cholesterol sensor.

FIG. 34 illustrates by, a block diagram, examples of signals obtainedfor measuring various biological variables such as glucose 600,cholesterol 602 and oxygen 604 in the manner as exemplified in FIGS.33A-33C. A glucose signal 606, a cholesterol signal 608 and an oxygensignal 610 are generated by transducers or sensors as shown in FIGS. 33Band 33C. The signals are transmitted to a multiplexer 612 whichtransmits the signals as a coded signal by wire 614 to a transmitter616. A coded and modulated signal is transmitted, as represented by line618, by radio, light, sound, wire telephone or the like with noisesuppression to a receiver 620. The signal is then amplified and filteredat amplifier and filter 622. The signal passes through a demultiplexer624 and the separated signals are amplified at 626, 628, 630,respectively and transmitted and displayed at display 632 of a CPU andrecorded for transmission by modem 634 to a hospital network, forexample.

FIGS. 35A-35C illustrate an intelligent contact lens being activated byclosure of the eyelids with subsequent increased diffusion of bloodcomponents to the sensor. During movement of the eye lids from theposition shown in FIG. 35C to the position shown in FIG. 35A by blinkingand/or closure of the eye, a combination of forces are applied to thecontact device 636 by the eyelid with a horizontal force (normal forcecomponent) of approximately 25,000 dynes which causes an intimateinteraction between the contact device and the surface of the eye with adisruption of the lipid layer of the tear film allowing directinteraction of the outer surface of the contact device with thepalpebral conjunctiva as well as a direct interaction of the innersurface of the contact device with the aqueous layer of the tear filmand the epithelial surface of the cornea and bulbar conjunctiva.Blinking promotes a pump system which extracts fluid from thesupero-temporal corner of the eye and delivery of fluid to the puncta inthe infero-medial comer of the eye creating a continuous flow whichbathes the contact device. During blinking, the close interaction withthe palpebral conjunctiva, bulbar conjunctiva, and cornea, the slightlyrugged surface of the contact device creates microdisruption of theblood barrier and of the epithelial surface with transudation andincreased flow of tissue fluid toward the surface of the contact device.The tear fluid then diffuses through the selectively permeable membraneslocated on the surface of the contact device 636 and subsequentlyreaching the electrodes of the sensor 638 mounted in the contact device.In the preferred embodiment for glucose measurement, glucose and oxygenflow from the capillary vessels 640 toward a selectively permeable outermembrane and subsequently reach a mid-membrane with immobilized glucoseoxidase enzyme. At this layer of immobilized glucose oxidase enzyme, anenzymatic oxidation of glucose in the presence of the enzyzme oxidaseand oxygen takes place with the formation of hydrogen peroxide andgluconic acid. The hydrogen peroxide then diffuses through an innermembrane and reaches the surface of a platinum electrode and it isoxidized on the surface of the working electrode creating a measurableelectrical current. The intensity of the current generated isproportional to the concentration of hydrogen peroxide which isproportional to the concentration of glucose. The electrical current issubsequently converted to a frequency audio signal by a transmittermounted in the contact device with signals being transmitted to a remotereceiver using preferably electromagnetic energy for subsequentamplification, decoding, processing, analysis, and display.

In FIGS. 36A through 36J, various shapes of contact devices are shownfor use in different situations. In FIG. 36A, a contact device 642 isshown of an elliptical, banana or half moon shape for placement underthe upper or lower eye lid. FIGS. 36B and 36C show a contact device 644having, in side view a wide base portion 646 as compared to an upperportion 648. FIG. 36D shows a contact device 650 having a truncated lensportion 652.

In FIGS. 36E and 36F, the contact device 654 is shown in side view inFIG. 36E and includes a widened base portion 656 which as shown in FIG.36F is of a semi-truncated configuration.

FIG. 36G shows a contact device 658, having a corneal portion 650 and ascleral portion 652. In FIG. 36H, an oversized contact device 664,includes a corneal portion 666 and a scleral portion 668.

A more circular shaped contact device 670 is shown in FIG. 36I having acorneal-scleral lens 672.

The contact device 674 shown in FIG. 36J is similar to the ones shown inFIGS. 32, 33A, 35A and 35C. The contact device includes a main bodyportion 676 with upper myoflange or minus carrier 678 and lowermyoflange or minus carrier 680.

In FIG. 37A, an upper contact device 682 is placed under an upper eyelid 684. Similarly, a lower contact device 686 is placed underneath alower eye lid 688. Upper contact device 682 includes an oxygensensor/transmitter 690 and a glucose transmitter 692. Similarly, thelower contact device includes a temperature sensor transmitter 694 and apH sensor/transmitter 696.

Each of these four sensors outputs a signal to respective receivers 698,700, 702 and 704, for subsequent display in CPU displays 706, 708, 710,712, respectively. The CPUs display an indication of a sensed oxygenoutput 714, temperature output 716, pH output 718 and glucose output720.

In FIG. 37B, a single contact device 722, in an hour glass shape,includes an upper sodium sensor/transmitter 724 and a lower potassiumsensor/transmitter 726. The two sensors send respective signals toreceivers 728 and 730 for display in CPUs 732, 734 for providing asodium output indicator 736 and a potassium output indicator 738.

In FIG. 38A, a contact device 740 is shown which may be formed of anannular band 742 so as to have a central opening with the openingoverlying a corneal portion or if the contact device includes a cornealportion, the corneal portion lays on the surface of the cornea. Limitedto annular band 742 is a sensor 744 positioned on the scleral portion ofthe contact device so as to be positioned under an eye lid. The sensoris connected by wires 746a, 746b to transmitter 748 which is incommunication with the power source 750 by wires 752a, 752b. Theintelligent contact lens device 740 is shown in section in FIG. 38B withthe power source 750 and sensor 744 located on opposite ends of thecontact device on the scleral portion of the contact device.

FIG. 39A schematically illustrates the flow of tear fluid as illustratedby arrows 754 from the right lacrimal gland 756 across the eye to thelacrimal punctum 758a and 758. Taking advantage of the flow of tearfluid, in FIG. 39B, a contact device 760 is positioned in the lowercul-de-sac 762 beneath the lower eye lid 764 so that a plurality ofsensors 764a, 764b and 764c in wire communication with a power source766 and transducer 768 can be connected by a wire 770 to an externaldevice. The flow of tear fluid from the left lacrimal gland 762 to thelacrimal punctum 764a and 764b is taken advantage of to produce areading indicative of the properties to be detected by the sensors.

In FIG. 40A, a contact device 772 is positioned in the cul-de-sac 774 ofthe lower eye lid 776. The contact device includes a needle-type glucosesensor 778 in communication with a transmitter 780 and a power source782. A signal 782 is transmitted to a receiver, demultiplexer andamplifier 784 for transmission to a CPU and modem 786 and subsequenttransmission over a public communication network 788 for receipt andappropriate action at an interface 790 of a hospital network.

In FIG. 40B, a similar arrangement to that shown in FIG. 40A is usedexcept the glucose sensor 792 is a needle type sensor with a curvedshape so as to be placed directly against the eye lid. The sensor 792 issilicone coated or encased by coating with silicone for comfortable wearunder the eye lid 794. Wires 796a and 796b extend from under the eye lidand are connected to an external device. The sensor 792 is placed indirect contact with the conjunctiva with signals and power sourceconnected by wires to external devices.

FIG. 41 shows an oversized contact device 798 including sensors 800a,800b, 800c and the scleral portion of the contact device to bepositioned under the upper eye lid. In addition, sensors 802a, 802b,802c are to be positioned under the lower eye lid in contact with thebulbar and/or palpebral conjunctiva. In addition, sensors 804a-d arelocated in the corneal portion in contact with the tear film over thecornea.

FIG. 42A shows a contact device 806 having a sensor 808 and atransmitter 810 in position, at rest, with the eye lids open. However,in FIG. 42B, when the eye lids move towards a closed position, and theindividual is approaching a state of sleep, the Bell phenomenon willmove the eye and therefore the contact device upward in the direction ofarrows 812. The pressure produced from the eye lid as the contact devicemoves up, will produce a signal 814 from the sensor 808 which istransmitted to a receive 816. The signal passes through an amplifier andfilter 818 to a demultiplexer 820 for activation of an alarm circuit 822and display of data at 824. The alarm should be sufficient to wake adozing driver or operator of other machinery to alert the user of signsof somnolence.

In FIG. 43, a heat stimulation transmission device 825 for externalplacement on the surface of the eye is shown for placement on thescleral and corneal portions of the eye. The device 825 includes aplurality of sensors 826 spaced across the device 825. With reference toFIG. 44, the device 825 includes heating elements 828a-c, a thermistor830, an oxygen sensor 832, and a preferably inductively activated powersource 834. Signals generated by the sensors are transmitted bytransmitter 836 to hardware 838 which provides an output representativeof a condition detected by the sensors.

In FIG. 46, an annular band 840 includes a plurality of devices 842a-e.The annular band shaped heat stimulation transmission device 840 can beused externally or internally by surgical implication in any part of thebody promoting increase of oxygen from a remotely situated stimulatingsource. Another surgically implantable device 844 is shown in FIG. 46.In this example, the heat stimulation transmission device 844 isimplanted between eye muscles 846, 848. Another example of a surgicallyimplantable heat stimulation transmission device 850 is shown in FIG.47, having four heating elements 852, a temperature sensor 854 and anoxygen sensor 856, with a power source 858 and a transmitter 860 fortransmitting signal 852.

FIGS. 48, 49 and 51 through 53 illustrate the use of an overheatingtransmission device, as shown in FIG. 50, for the destruction of tumorcells after the implantation of the overheating transmission device bysurgery. As shown in FIG. 50, the overheating transmission device 864includes a plurality of heating elements 866a, 866b, 866c, a temperaturesensor 868, a power source 870 which is inductively activated and atransmitter 872 for transmitting a signal 874. By activation of thedevice 864, an increase in temperature results in the immediatelyadjacent area. This can cause the destruction of tumor cells from aremote location.

In FIG. 48, the device 864 is located adjacent to a brain tumor 876. InFIG. 49, the device 864 is located adjacent to a kidney tumor 878.

In FIG. 51, the device 864 is located adjacent to an intraocular tumor880. In FIG. 52, a plurality of devices 864 are located adjacent to alung tumor 882. In FIG. 53, a device 864 is located externally on thebreast, adjacent to a breast tumor 884.

In FIGS. 54A and 54B, a contact device 886 is located on the eye 888.The contact device is used to detect glucose in the aqueous humor byemitting light from light emitting optical fiber 890, which is sensitiveto glucose, as compared to a reference optical fiber light source 892,which is not sensitive to glucose. Two photo detectors 894a, 894bmeasure the amount of light passing from the reference optical fiber 892and the emitting optical fiber 890 sensitive to glucose and transmit thereceived signals by wires 896a, 896b for analysis.

In FIG. 54C, a glucose detecting contact device 900 is used having apower source 902, an emitting light source 904 sensitive to glucose anda reference light source 906, non-sensitive to glucose. Two photodetectors 908a and 908b, provide a signal to a transmitter 910 fortransmission of a signal 912 to a remote location for analysis andstorage.

In FIG. 55A, a contact device 914 is positioned on an eye 916 fordetection of heart pulsations or heart sounds as transmitted to eye 916by the heart 918 as a normal bodily function. A transmitter provides asignal 920 indicative of the results of the heart pulsations or heartsound. A remote alarm device 922 may be worn by the individual. Thedetails of the alarm device are shown in FIG. 55B where the receiver 924receives the transmitted signal 920 and conveys the signal to a displaydevice 926 as well as to an alarm circuit 928 for activation of an alarmif predetermined parameters are exceeded.

In FIG. 56, a contact device 930 is shown. The contact device includesan ultra sound sensor 932, a power source 934 and a transmitter 936 forconveying a signal 938. The ultra sound sensor 932 is placed on a bloodvessel 940 for measurement of blood flow and blood velocity. The resultof this analysis is transmitted by signal 938 to a remote receiver foranalysis and storage.

In FIG. 57, an oversized contact device 940 includes a sensor 942, apower source 944 and a transmitter 946 for transmitting a signal 948.The sensor 942 is positioned on the superior rectus muscle formeasurement of eye muscle potential. The measured potential istransmitted by signal 948 to a remote receiver for analysis and storage.

In FIG. 58A, a contact device 950 includes a light source 952, a powersource 954, multioptical filter system 956 and a transmitter 958 fortransmission of a signal 960. The light source 952 emits a beam of lightto the optic nerve head 962. The beam of light is reflected on to themultioptical filter system 956 for determination of the angle ofreflection.

As shown in FIG. 58B, since the distance X of separation between themultioptical filter system and the head of the optic nerve 962 remainsconstant as does the separation distance Y between the light source 952and the multoptical filter system 956, a change in the point P which isrepresentative of the head of the optic nerve will cause a consequentchange in the angle of reflection so that the reflected light will reacha different point on the multioptical filter system 956. The change ofthe reflection point on multioptical filter system 956 will create acorresponding voltage change based on the reflection angle. The voltagesignal is transmitted as an audio frequency signal 960 to a remotelocation for analysis and storage.

In FIGS. 59A through 59C, a neuro stimulation transmission device 964 isshown. In FIG. 59A, the device 964 is surgically implanted in the brain966. The device 964 includes microphotodiodes or electrodes 968 and apower source/transmitter 970. The device is implanted adjacent to theoccipital cortex 972.

In FIG. 59B, the device 964 is surgically implanted in the eye 974 on aband 976 including microphotodiodes 978a, 978b with a power source 980and a transmitter 982.

In FIG. 59C, the device 964 is externally placed on the eye 974 using anoversized contact device 984 as a corneal scleral lens. The deviceincludes an electrode 986 producing a microcurrent, a microphotodiode orelectrode 988, a power source 990 and a transmitter 992 for transmissionof a signal to a remote location for analysis and storage.

In FIG. 60, a contact device 1000 includes a power source 1002 and afixed frequency transmitter 1004. The transmitter 1004 emits a frequencywhich is received by an orbiting satellite 1006. Upon detection of thefrequency of the signal transmitted by the transmitter 1004, thesatellite can transmit a signal for remote reception indicative of thelocation of the transmitter 1004 and accordingly the exact location ofthe individual wearing the contact device 1000. This would be useful inmilitary operations to constantly monitor the location of all personal.

In FIG. 61, a contact device 1008 is located below the lower eye lid1010. The contact device includes a pressure sensor, an integratedcircuit 1012, connected to an LED drive 1014 and an LED 1016. A powersource 1018 is associated with the device located in the contact device1008.

By closure of the eye 1020 by the eye lids, the pressure sensor 1012would be activated to energize the LED drive and therefore the LED fortransmission of a signal 1020 to a remote photodiode or optical receiver1022 located on a receptor system. The photodiode or optical receiver1022, upon receipt of the signal 1020, can transmit a signal 1024 forturning on or off a circuit. This application has may uses for thoseindividuals limited in their body movement to only their eyes.

In FIG. 62, a contact device 1026 includes compartments 1028, 1030 whichinclude a chemical or drug which can be dispensed at the location of thecontact device 1026. The sensor 1032 provides an signal indicative of aspecific condition or parameter to be measured. Based upon the resultsof the analysis of this signal, when warranted, by logic circuit 1034, aheater device 1036 can be activated to melt a thread or other closuremember 1038 sealing the compartments 1028, 1030 so as to allow releaseof the chemical or drug contained in the compartments 1028, 1030. Thesystem is powered by power source 1040 based upon the biologicalvariable signal generated as a result of measurement by sensor 1032.

According to the system shown in FIG. 63, a glucose sensor 1042,positioned on the eye 1044, can generate a glucose level signal 1046 toa receiver 1048 associated with an insulin pump 1050 for release ofinsulin into the blood stream 1052. The associated increase in insulinwill again be measured on the eye 1044 by the sensor 1042 so as tocontrol the amount of insulin released by the insulin pump 1050. Aconstant monitoring system is thereby established

While the present invention has been described with reference topreferred embodiments thereof, it is understood that the presentinvention is not limited to those embodiments, and by the scope of theappended claims.

I claim:
 1. A contact device for placement in contact with an eye, saidcontact device comprising:a contact surface for engagement with asurface of the eye, a sensor mounted on said contact surface, saidcontact surface being positionable so that eye fluids encounter saidsensor, said sensor generating a signal indicative of chemicalparameters of a body and the eye based upon eye fluids encountered bythe sensor, said signal being transmitted externally of the eye foranalysis of the signal and indication of a status of certain bodilyfunctions, a signal transmitter mounted on said contact surface fortransmitting said signal, and an energy source for powering said signaltransmitter.
 2. A contact device as claimed in claim 1, wherein thesignal is transmitted through the air by said signal transmitter forreceipt at a remote location.
 3. A contact device as claimed in claim 1,wherein said sensor detects glucose levels in the eye fluid.
 4. Acontact device as claimed in claim 1, wherein said sensor detectscholesterol levels in the eye fluid.
 5. A contact device as claimed inclaim 1, wherein said sensor detects oxygen levels in the eye fluid. 6.A contact device as claimed in claim 1, wherein said sensor detects pHlevels in the eye fluid.
 7. A contact device as claimed in claim 1,wherein said sensor detects potassium levels in the eye fluid.
 8. Acontact device as claimed in claim 1, wherein said sensor detects sodiumlevels in the eye fluid.
 9. A contact device for placement in contactwith an eye, said contact device comprising:a contact surface forengaging a surface of the eye, and a sensor mounted on said contactsurface, said sensor being positionable under an eye lid of the eyes,said sensor being a pressure sensor responsive to pressure intentionallyimposed on said sensor by closing the eye lids for a predeterminedperiod of time necessary to activate an electrical circuit forperforming a function.
 10. A contact device as claimed in claim 9,wherein a light emitting diode mounted on said contact surface isactivated by intentional closure of the eye lids for a predeterminedperiod of time.
 11. A contact device for placement in contact with aneye, said contact device comprising:a contact surface for engaging asurface of the eye, a sensor mounted on said contact surface, saidsensor producing a signal indicative of a bodily function, said signalbeing transmitted away from the eye for analysis and indication of astatus of the bodily function, and a heater and a storage compartmentmounted on said contact surface, said storage compartment includingchemicals or drugs for release upon activation of said heater based uponsaid signal produced by said sensor.
 12. A contact device as claimed inclaim 11, wherein a light source is mounted on said contact surface, andsaid sensor detects light emitted from the light source.
 13. A contactdevice for placement in contact with an eye, said contact devicecomprising:a contact surface for engagement with a portion of the eye,and a sensor mounted on said contact surface, said contact surface beingpositionable so that bodily fluids encounter said sensor, said sensorgenerating a signal indicative of a property of the encountered bodilyfluids, said signal being transmitted externally of the live body foranalysis of the signal and indication of a status of certain bodilyfunctions, said sensor being responsive to the eye lid when the eyelidsare moved into a position caused by sleeping of the individual wearingthe contact device, a signal being generated by said sensor when closingeye lids indicative of sleep, said signal being transmitted to an alarmcircuit for alerting the individual of the transition of the individualto a sleep state.
 14. A contact device for placement in contact with aneye, said contact device comprising:a contact surface for engaging asurface of the eye, a sensor mounted on said contact surface, saidsensor producing a signal indicative of a bodily function, said signalbeing transmitted away from the eye for analysis and indication of astatus of the bodily function, and a pump for injecting an individualwith medication based upon the signal generated by said sensor.
 15. Acontact device for placement in contact with an eye and eyelids, saidcontact device comprising:opposed contact surfaces for engagement with aportion of the eye and the eyelids, a sensor mounted on one of saidcontact surfaces, a sensor selective membrane surface of said sensor forpassage therethrough of fluid from the eye, an electrode of said sensorpositioned internally of said sensor selective membrane between saidopposed contact surfaces, a signal generated by said electrodeindicative of a property of the fluid from the eye, a transmitterlocated between said contact surfaces for transmitting said signalexternally of the eye and the eye lids for analysis of the signal andindication of a status of certain bodily functions.
 16. A contact deviceas claimed in claim 15, wherein said sensor detects glucose levels inthe fluid from of the eye.
 17. A contact device as claimed in claim 15,wherein said sensor detects cholesterol levels in the fluid from theeye.
 18. A contact device as claimed in claim 15, wherein said sensordetects oxygen levels in the fluid from the eye.
 19. A contact device asclaimed in claim 15, wherein said sensor detects a temperature level inthe fluid from the eye.
 20. A contact device as claimed in claim 15,wherein said sensor detects potassium levels in the fluid from the eye.21. A contact device as claimed in claim 15, wherein said sensor detectssodium levels in the fluid from the eye.
 22. A contact device as claimedin claim 15, wherein the signal is transmitted through the air by saidtransmitter for receipt at a remote location.